vmbus.c

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/*
 * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */
 
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
/** @file
 *
 * Hyper-V virtual machine bus
 *
 */
 
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <ipxe/nap.h>
#include <ipxe/malloc.h>
#include <ipxe/iobuf.h>
#include <ipxe/bitops.h>
#include <ipxe/hyperv.h>
#include <ipxe/vmbus.h>
 
/** VMBus initial GPADL ID
 *
 * This is an opaque value with no meaning.  The Linux kernel uses
 * 0xe1e10.
 */
#define VMBUS_GPADL_MAGIC 0x18ae0000
 
/** Current (i.e. most recently issued) GPADL ID */
static unsigned int vmbus_gpadl = VMBUS_GPADL_MAGIC;
 
/** Obsolete GPADL ID threshold
 *
 * When the Hyper-V connection is reset, any previous GPADLs are
 * automatically rendered obsolete.
 */
unsigned int vmbus_obsolete_gpadl;
 
/**
 * Post message
 *
 * @v hv                Hyper-V hypervisor
 * @v header            Message header
 * @v len               Length of message (including header)
 * @ret rc              Return status code
 */
static int vmbus_post_message ( struct hv_hypervisor *hv,
                                const struct vmbus_message_header *header,
                                size_t len ) {
        struct vmbus *vmbus = hv->vmbus;
        int rc;
 
        /* Post message */
        if ( ( rc = hv_post_message ( hv, VMBUS_MESSAGE_ID, VMBUS_MESSAGE_TYPE,
                                      header, len ) ) != 0 ) {
                DBGC ( vmbus, "VMBUS %p could not post message: %s\n",
                       vmbus, strerror ( rc ) );
                return rc;
        }
 
        return 0;
}
 
/**
 * Post empty message
 *
 * @v hv                Hyper-V hypervisor
 * @v type              Message type
 * @ret rc              Return status code
 */
static int vmbus_post_empty_message ( struct hv_hypervisor *hv,
                                      unsigned int type ) {
        struct vmbus_message_header header = { .type = cpu_to_le32 ( type ) };
 
        return vmbus_post_message ( hv, &header, sizeof ( header ) );
}
 
/**
 * Wait for received message of any type
 *
 * @v hv                Hyper-V hypervisor
 * @ret rc              Return status code
 */
static int vmbus_wait_for_any_message ( struct hv_hypervisor *hv ) {
        struct vmbus *vmbus = hv->vmbus;
        int rc;
 
        /* Wait for message */
        if ( ( rc = hv_wait_for_message ( hv, VMBUS_MESSAGE_SINT ) ) != 0 ) {
                DBGC ( vmbus, "VMBUS %p failed waiting for message: %s\n",
                       vmbus, strerror ( rc ) );
                return rc;
        }
 
        /* Sanity check */
        if ( hv->message->received.type != cpu_to_le32 ( VMBUS_MESSAGE_TYPE ) ){
                DBGC ( vmbus, "VMBUS %p invalid message type %d\n",
                       vmbus, le32_to_cpu ( hv->message->received.type ) );
                return -EINVAL;
        }
 
        return 0;
}
 
/**
 * Wait for received message of a specified type, ignoring any others
 *
 * @v hv                Hyper-V hypervisor
 * @v type              Message type
 * @ret rc              Return status code
 */
static int vmbus_wait_for_message ( struct hv_hypervisor *hv,
                                    unsigned int type ) {
        struct vmbus *vmbus = hv->vmbus;
        const struct vmbus_message_header *header = &vmbus->message->header;
        int rc;
 
        /* Loop until specified message arrives, or until an error occurs */
        while ( 1 ) {
 
                /* Wait for message */
                if ( ( rc = vmbus_wait_for_any_message ( hv ) ) != 0 )
                        return rc;
 
                /* Check for requested message type */
                if ( header->type == cpu_to_le32 ( type ) )
                        return 0;
 
                /* Ignore any other messages (e.g. due to additional
                 * channels being offered at runtime).
                 */
                DBGC ( vmbus, "VMBUS %p ignoring message type %d (expecting "
                       "%d)\n", vmbus, le32_to_cpu ( header->type ), type );
        }
}
 
/**
 * Initiate contact
 *
 * @v hv                Hyper-V hypervisor
 * @v raw               VMBus protocol (raw) version
 * @ret rc              Return status code
 */
static int vmbus_initiate_contact ( struct hv_hypervisor *hv,
                                    unsigned int raw ) {
        struct vmbus *vmbus = hv->vmbus;
        const struct vmbus_version_response *version = &vmbus->message->version;
        struct vmbus_initiate_contact initiate;
        int rc;
 
        /* Construct message */
        memset ( &initiate, 0, sizeof ( initiate ) );
        initiate.header.type = cpu_to_le32 ( VMBUS_INITIATE_CONTACT );
        initiate.version.raw = cpu_to_le32 ( raw );
        initiate.intr = virt_to_phys ( vmbus->intr );
        initiate.monitor_in = virt_to_phys ( vmbus->monitor_in );
        initiate.monitor_out = virt_to_phys ( vmbus->monitor_out );
 
        /* Post message */
        if ( ( rc = vmbus_post_message ( hv, &initiate.header,
                                         sizeof ( initiate ) ) ) != 0 )
                return rc;
 
        /* Wait for response */
        if ( ( rc = vmbus_wait_for_message ( hv, VMBUS_VERSION_RESPONSE ) ) !=0)
                return rc;
 
        /* Check response */
        if ( ! version->supported ) {
                DBGC ( vmbus, "VMBUS %p requested version not supported\n",
                       vmbus );
                return -ENOTSUP;
        }
 
        DBGC ( vmbus, "VMBUS %p initiated contact using version %d.%d\n",
               vmbus, le16_to_cpu ( initiate.version.major ),
               le16_to_cpu ( initiate.version.minor ) );
        return 0;
}
 
/**
 * Terminate contact
 *
 * @v hv                Hyper-V hypervisor
 * @ret rc              Return status code
 */
static int vmbus_unload ( struct hv_hypervisor *hv ) {
        int rc;
 
        /* Post message */
        if ( ( rc = vmbus_post_empty_message ( hv, VMBUS_UNLOAD ) ) != 0 )
                return rc;
 
        /* Wait for response */
        if ( ( rc = vmbus_wait_for_message ( hv, VMBUS_UNLOAD_RESPONSE ) ) != 0)
                return rc;
 
        return 0;
}
 
/**
 * Negotiate protocol version
 *
 * @v hv                Hyper-V hypervisor
 * @ret rc              Return status code
 */
static int vmbus_negotiate_version ( struct hv_hypervisor *hv ) {
        int rc;
 
        /* We require the ability to disconnect from and reconnect to
         * VMBus; if we don't have this then there is no (viable) way
         * for a loaded operating system to continue to use any VMBus
         * devices.  (There is also a small but non-zero risk that the
         * host will continue to write to our interrupt and monitor
         * pages, since the VMBUS_UNLOAD message in earlier versions
         * is essentially a no-op.)
         *
         * This requires us to ensure that the host supports protocol
         * version 3.0 (VMBUS_VERSION_WIN8_1).  However, we can't
         * actually _use_ protocol version 3.0, since doing so causes
         * an iSCSI-booted Windows Server 2012 R2 VM to crash due to a
         * NULL pointer dereference in vmbus.sys.
         *
         * To work around this problem, we first ensure that we can
         * connect using protocol v3.0, then disconnect and reconnect
         * using the oldest known protocol.
         */
 
        /* Initiate contact to check for required protocol support */
        if ( ( rc = vmbus_initiate_contact ( hv, VMBUS_VERSION_WIN8_1 ) ) != 0 )
                return rc;
 
        /* Terminate contact */
        if ( ( rc = vmbus_unload ( hv ) ) != 0 )
                return rc;
 
        /* Reinitiate contact using the oldest known protocol version */
        if ( ( rc = vmbus_initiate_contact ( hv, VMBUS_VERSION_WS2008 ) ) != 0 )
                return rc;
 
        return 0;
}
 
/**
 * Establish GPA descriptor list
 *
 * @v vmdev             VMBus device
 * @v data              Data buffer
 * @v len               Length of data buffer
 * @ret gpadl           GPADL ID, or negative error
 */
int vmbus_establish_gpadl ( struct vmbus_device *vmdev, void *data,
                            size_t len ) {
        struct hv_hypervisor *hv = vmdev->hv;
        struct vmbus *vmbus = hv->vmbus;
        physaddr_t addr = virt_to_phys ( data );
        unsigned int pfn_count = hv_pfn_count ( addr, len );
        struct {
                struct vmbus_gpadl_header gpadlhdr;
                struct vmbus_gpa_range range;
                uint64_t pfn[pfn_count];
        } __attribute__ (( packed )) gpadlhdr;
        const struct vmbus_gpadl_created *created = &vmbus->message->created;
        unsigned int gpadl;
        unsigned int i;
        int rc;
 
        /* Allocate GPADL ID */
        gpadl = ++vmbus_gpadl;
 
        /* Construct message */
        memset ( &gpadlhdr, 0, sizeof ( gpadlhdr ) );
        gpadlhdr.gpadlhdr.header.type = cpu_to_le32 ( VMBUS_GPADL_HEADER );
        gpadlhdr.gpadlhdr.channel = cpu_to_le32 ( vmdev->channel );
        gpadlhdr.gpadlhdr.gpadl = cpu_to_le32 ( gpadl );
        gpadlhdr.gpadlhdr.range_len =
                cpu_to_le16 ( ( sizeof ( gpadlhdr.range ) +
                                sizeof ( gpadlhdr.pfn ) ) );
        gpadlhdr.gpadlhdr.range_count = cpu_to_le16 ( 1 );
        gpadlhdr.range.len = cpu_to_le32 ( len );
        gpadlhdr.range.offset = cpu_to_le32 ( addr & ( PAGE_SIZE - 1 ) );
        for ( i = 0 ; i < pfn_count ; i++ )
                gpadlhdr.pfn[i] = ( ( addr / PAGE_SIZE ) + i );
 
        /* Post message */
        if ( ( rc = vmbus_post_message ( hv, &gpadlhdr.gpadlhdr.header,
                                         sizeof ( gpadlhdr ) ) ) != 0 )
                return rc;
 
        /* Wait for response */
        if ( ( rc = vmbus_wait_for_message ( hv, VMBUS_GPADL_CREATED ) ) != 0 )
                return rc;
 
        /* Check response */
        if ( created->channel != cpu_to_le32 ( vmdev->channel ) ) {
                DBGC ( vmdev, "VMBUS %s unexpected GPADL channel %d\n",
                       vmdev->dev.name, le32_to_cpu ( created->channel ) );
                return -EPROTO;
        }
        if ( created->gpadl != cpu_to_le32 ( gpadl ) ) {
                DBGC ( vmdev, "VMBUS %s unexpected GPADL ID %#08x\n",
                       vmdev->dev.name, le32_to_cpu ( created->gpadl ) );
                return -EPROTO;
        }
        if ( created->status != 0 ) {
                DBGC ( vmdev, "VMBUS %s GPADL creation failed: %#08x\n",
                       vmdev->dev.name, le32_to_cpu ( created->status ) );
                return -EPROTO;
        }
 
        DBGC ( vmdev, "VMBUS %s GPADL %#08x is [%08lx,%08lx)\n",
               vmdev->dev.name, gpadl, addr, ( addr + len ) );
        return gpadl;
}
 
/**
 * Tear down GPA descriptor list
 *
 * @v vmdev             VMBus device
 * @v gpadl             GPADL ID
 * @ret rc              Return status code
 */
int vmbus_gpadl_teardown ( struct vmbus_device *vmdev, unsigned int gpadl ) {
        struct hv_hypervisor *hv = vmdev->hv;
        struct vmbus *vmbus = hv->vmbus;
        struct vmbus_gpadl_teardown teardown;
        const struct vmbus_gpadl_torndown *torndown = &vmbus->message->torndown;
        int rc;
 
        /* If GPADL is obsolete (i.e. was created before the most
         * recent Hyper-V reset), then we will never receive a
         * response to the teardown message.  Since the GPADL is
         * already destroyed as far as the hypervisor is concerned, no
         * further action is required.
         */
        if ( vmbus_gpadl_is_obsolete ( gpadl ) )
                return 0;
 
        /* Construct message */
        memset ( &teardown, 0, sizeof ( teardown ) );
        teardown.header.type = cpu_to_le32 ( VMBUS_GPADL_TEARDOWN );
        teardown.channel = cpu_to_le32 ( vmdev->channel );
        teardown.gpadl = cpu_to_le32 ( gpadl );
 
        /* Post message */
        if ( ( rc = vmbus_post_message ( hv, &teardown.header,
                                         sizeof ( teardown ) ) ) != 0 )
                return rc;
 
        /* Wait for response */
        if ( ( rc = vmbus_wait_for_message ( hv, VMBUS_GPADL_TORNDOWN ) ) != 0 )
                return rc;
 
        /* Check response */
        if ( torndown->gpadl != cpu_to_le32 ( gpadl ) ) {
                DBGC ( vmdev, "VMBUS %s unexpected GPADL ID %#08x\n",
                       vmdev->dev.name, le32_to_cpu ( torndown->gpadl ) );
                return -EPROTO;
        }
 
        return 0;
}
 
/**
 * Open VMBus channel
 *
 * @v vmdev             VMBus device
 * @v op                Channel operations
 * @v out_len           Outbound ring buffer length
 * @v in_len            Inbound ring buffer length
 * @v mtu               Maximum expected data packet length (including headers)
 * @ret rc              Return status code
 *
 * Both outbound and inbound ring buffer lengths must be a power of
 * two and a multiple of PAGE_SIZE.  The requirement to be a power of
 * two is a policy decision taken to simplify the ring buffer indexing
 * logic.
 */
int vmbus_open ( struct vmbus_device *vmdev,
                 struct vmbus_channel_operations *op,
                 size_t out_len, size_t in_len, size_t mtu ) {
        struct hv_hypervisor *hv = vmdev->hv;
        struct vmbus *vmbus = hv->vmbus;
        struct vmbus_open_channel open;
        const struct vmbus_open_channel_result *opened =
                &vmbus->message->opened;
        size_t len;
        void *ring;
        void *packet;
        int gpadl;
        uint32_t open_id;
        int rc;
 
        /* Sanity checks */
        assert ( ( out_len % PAGE_SIZE ) == 0 );
        assert ( ( out_len & ( out_len - 1 ) ) == 0 );
        assert ( ( in_len % PAGE_SIZE ) == 0 );
        assert ( ( in_len & ( in_len - 1 ) ) == 0 );
        assert ( mtu >= ( sizeof ( struct vmbus_packet_header ) +
                          sizeof ( struct vmbus_packet_footer ) ) );
 
        /* Allocate packet buffer */
        packet = malloc ( mtu );
        if ( ! packet ) {
                rc = -ENOMEM;
                goto err_alloc_packet;
        }
 
        /* Allocate ring buffer */
        len = ( sizeof ( *vmdev->out ) + out_len +
                sizeof ( *vmdev->in ) + in_len );
        assert ( ( len % PAGE_SIZE ) == 0 );
        ring = malloc_phys ( len, PAGE_SIZE );
        if ( ! ring ) {
                rc = -ENOMEM;
                goto err_alloc_ring;
        }
        memset ( ring, 0, len );
 
        /* Establish GPADL for ring buffer */
        gpadl = vmbus_establish_gpadl ( vmdev, ring, len );
        if ( gpadl < 0 ) {
                rc = gpadl;
                goto err_establish;
        }
 
        /* Construct message */
        memset ( &open, 0, sizeof ( open ) );
        open.header.type = cpu_to_le32 ( VMBUS_OPEN_CHANNEL );
        open.channel = cpu_to_le32 ( vmdev->channel );
        open_id = random();
        open.id = open_id; /* Opaque random value: endianness irrelevant */
        open.gpadl = cpu_to_le32 ( gpadl );
        open.out_pages = ( ( sizeof ( *vmdev->out ) / PAGE_SIZE ) +
                           ( out_len / PAGE_SIZE ) );
 
        /* Post message */
        if ( ( rc = vmbus_post_message ( hv, &open.header,
                                         sizeof ( open ) ) ) != 0 )
                goto err_post_message;
 
        /* Wait for response */
        if ( ( rc = vmbus_wait_for_message ( hv,
                                             VMBUS_OPEN_CHANNEL_RESULT ) ) != 0)
                goto err_wait_for_message;
 
        /* Check response */
        if ( opened->channel != cpu_to_le32 ( vmdev->channel ) ) {
                DBGC ( vmdev, "VMBUS %s unexpected opened channel %#08x\n",
                       vmdev->dev.name, le32_to_cpu ( opened->channel ) );
                rc = -EPROTO;
                goto err_check_response;
        }
        if ( opened->id != open_id /* Non-endian */ ) {
                DBGC ( vmdev, "VMBUS %s unexpected open ID %#08x\n",
                       vmdev->dev.name, le32_to_cpu ( opened->id ) );
                rc = -EPROTO;
                goto err_check_response;
        }
        if ( opened->status != 0 ) {
                DBGC ( vmdev, "VMBUS %s open failed: %#08x\n",
                       vmdev->dev.name, le32_to_cpu ( opened->status ) );
                rc = -EPROTO;
                goto err_check_response;
        }
 
        /* Store channel parameters */
        vmdev->out_len = out_len;
        vmdev->in_len = in_len;
        vmdev->out = ring;
        vmdev->in = ( ring + sizeof ( *vmdev->out ) + out_len );
        vmdev->gpadl = gpadl;
        vmdev->op = op;
        vmdev->mtu = mtu;
        vmdev->packet = packet;
 
        DBGC ( vmdev, "VMBUS %s channel GPADL %#08x ring "
                "[%#08lx,%#08lx,%#08lx)\n", vmdev->dev.name, vmdev->gpadl,
                virt_to_phys ( vmdev->out ), virt_to_phys ( vmdev->in ),
                ( virt_to_phys ( vmdev->out ) + len ) );
        return 0;
 
 err_check_response:
 err_wait_for_message:
 err_post_message:
        vmbus_gpadl_teardown ( vmdev, vmdev->gpadl );
 err_establish:
        free_phys ( ring, len );
 err_alloc_ring:
        free ( packet );
 err_alloc_packet:
        return rc;
}
 
/**
 * Close VMBus channel
 *
 * @v vmdev             VMBus device
 */
void vmbus_close ( struct vmbus_device *vmdev ) {
        struct hv_hypervisor *hv = vmdev->hv;
        struct vmbus_close_channel close;
        size_t len;
        int rc;
 
        /* Construct message */
        memset ( &close, 0, sizeof ( close ) );
        close.header.type = cpu_to_le32 ( VMBUS_CLOSE_CHANNEL );
        close.channel = cpu_to_le32 ( vmdev->channel );
 
        /* Post message */
        if ( ( rc = vmbus_post_message ( hv, &close.header,
                                         sizeof ( close ) ) ) != 0 ) {
                DBGC ( vmdev, "VMBUS %s failed to close: %s\n",
                       vmdev->dev.name, strerror ( rc ) );
                /* Continue to attempt to tear down GPADL, so that our
                 * memory is no longer accessible by the remote VM.
                 */
        }
 
        /* Tear down GPADL */
        if ( ( rc = vmbus_gpadl_teardown ( vmdev, vmdev->gpadl ) ) != 0 ) {
                DBGC ( vmdev, "VMBUS %s failed to tear down channel GPADL: "
                       "%s\n", vmdev->dev.name, strerror ( rc ) );
                /* We can't prevent the remote VM from continuing to
                 * access this memory, so leak it.
                 */
                return;
        }
 
        /* Free ring buffer */
        len = ( sizeof ( *vmdev->out ) + vmdev->out_len +
                sizeof ( *vmdev->in ) + vmdev->in_len );
        free_phys ( vmdev->out, len );
        vmdev->out = NULL;
        vmdev->in = NULL;
 
        /* Free packet buffer */
        free ( vmdev->packet );
        vmdev->packet = NULL;
 
        DBGC ( vmdev, "VMBUS %s closed\n", vmdev->dev.name );
}
 
/**
 * Signal channel via monitor page
 *
 * @v vmdev             VMBus device
 */
static void vmbus_signal_monitor ( struct vmbus_device *vmdev ) {
        struct hv_hypervisor *hv = vmdev->hv;
        struct vmbus *vmbus = hv->vmbus;
        struct hv_monitor_trigger *trigger;
        unsigned int group;
        unsigned int bit;
 
        /* Set bit in monitor trigger group */
        group = ( vmdev->monitor / ( 8 * sizeof ( trigger->pending ) ));
        bit = ( vmdev->monitor % ( 8 * sizeof ( trigger->pending ) ) );
        trigger = &vmbus->monitor_out->trigger[group];
        set_bit ( bit, trigger );
}
 
/**
 * Signal channel via hypervisor event
 *
 * @v vmdev             VMBus device
 */
static void vmbus_signal_event ( struct vmbus_device *vmdev ) {
        struct hv_hypervisor *hv = vmdev->hv;
        int rc;
 
        /* Signal hypervisor event */
        if ( ( rc = hv_signal_event ( hv, VMBUS_EVENT_ID, 0 ) ) != 0 ) {
                DBGC ( vmdev, "VMBUS %s could not signal event: %s\n",
                       vmdev->dev.name, strerror ( rc ) );
                return;
        }
}
 
/**
 * Fill outbound ring buffer
 *
 * @v vmdev             VMBus device
 * @v prod              Producer index
 * @v data              Data
 * @v len               Length
 * @ret prod            New producer index
 *
 * The caller must ensure that there is sufficient space in the ring
 * buffer.
 */
static size_t vmbus_produce ( struct vmbus_device *vmdev, size_t prod,
                              const void *data, size_t len ) {
        size_t first;
        size_t second;
 
        /* Determine fragment lengths */
        first = ( vmdev->out_len - prod );
        if ( first > len )
                first = len;
        second = ( len - first );
 
        /* Copy fragment(s) */
        memcpy ( &vmdev->out->data[prod], data, first );
        if ( second )
                memcpy ( &vmdev->out->data[0], ( data + first ), second );
 
        return ( ( prod + len ) & ( vmdev->out_len - 1 ) );
}
 
/**
 * Consume inbound ring buffer
 *
 * @v vmdev             VMBus device
 * @v cons              Consumer index
 * @v data              Data buffer, or NULL
 * @v len               Length to consume
 * @ret cons            New consumer index
 */
static size_t vmbus_consume ( struct vmbus_device *vmdev, size_t cons,
                              void *data, size_t len ) {
        size_t first;
        size_t second;
 
        /* Determine fragment lengths */
        first = ( vmdev->in_len - cons );
        if ( first > len )
                first = len;
        second = ( len - first );
 
        /* Copy fragment(s) */
        memcpy ( data, &vmdev->in->data[cons], first );
        if ( second )
                memcpy ( ( data + first ), &vmdev->in->data[0], second );
 
        return ( ( cons + len ) & ( vmdev->in_len - 1 ) );
}
 
/**
 * Send packet via ring buffer
 *
 * @v vmdev             VMBus device
 * @v header            Packet header
 * @v data              Data
 * @v len               Length of data
 * @ret rc              Return status code
 *
 * Send a packet via the outbound ring buffer.  All fields in the
 * packet header must be filled in, with the exception of the total
 * packet length.
 */
static int vmbus_send ( struct vmbus_device *vmdev,
                        struct vmbus_packet_header *header,
                        const void *data, size_t len ) {
        struct hv_hypervisor *hv = vmdev->hv;
        struct vmbus *vmbus = hv->vmbus;
        static uint8_t padding[ 8 - 1 ];
        struct vmbus_packet_footer footer;
        size_t header_len;
        size_t pad_len;
        size_t footer_len;
        size_t ring_len;
        size_t cons;
        size_t prod;
        size_t old_prod;
        size_t fill;
 
        /* Sanity check */
        assert ( vmdev->out != NULL );
 
        /* Calculate lengths */
        header_len = ( le16_to_cpu ( header->hdr_qlen ) * 8 );
        pad_len = ( ( -len ) & ( 8 - 1 ) );
        footer_len = sizeof ( footer );
        ring_len = ( header_len + len + pad_len + footer_len );
 
        /* Check that we have enough room in the outbound ring buffer */
        cons = le32_to_cpu ( vmdev->out->cons );
        prod = le32_to_cpu ( vmdev->out->prod );
        old_prod = prod;
        fill = ( ( prod - cons ) & ( vmdev->out_len - 1 ) );
        if ( ( fill + ring_len ) >= vmdev->out_len ) {
                DBGC ( vmdev, "VMBUS %s ring buffer full\n", vmdev->dev.name );
                return -ENOBUFS;
        }
 
        /* Complete header */
        header->qlen = cpu_to_le16 ( ( ring_len - footer_len ) / 8 );
 
        /* Construct footer */
        footer.reserved = 0;
        footer.prod = vmdev->out->prod;
 
        /* Copy packet to buffer */
        DBGC2 ( vmdev, "VMBUS %s sending:\n", vmdev->dev.name );
        DBGC2_HDA ( vmdev, prod, header, header_len );
        prod = vmbus_produce ( vmdev, prod, header, header_len );
        DBGC2_HDA ( vmdev, prod, data, len );
        prod = vmbus_produce ( vmdev, prod, data, len );
        prod = vmbus_produce ( vmdev, prod, padding, pad_len );
        DBGC2_HDA ( vmdev, prod, &footer, sizeof ( footer ) );
        prod = vmbus_produce ( vmdev, prod, &footer, sizeof ( footer ) );
        assert ( ( ( prod - old_prod ) & ( vmdev->out_len - 1 ) ) == ring_len );
 
        /* Update producer index */
        wmb();
        vmdev->out->prod = cpu_to_le32 ( prod );
 
        /* Return if we do not need to signal the host.  This follows
         * the logic of hv_need_to_signal() in the Linux driver.
         */
        mb();
        if ( vmdev->out->intr_mask )
                return 0;
        rmb();
        cons = le32_to_cpu ( vmdev->out->cons );
        if ( cons != old_prod )
                return 0;
 
        /* Set channel bit in interrupt page */
        set_bit ( vmdev->channel, vmbus->intr->out );
 
        /* Signal the host */
        vmdev->signal ( vmdev );
 
        return 0;
}
 
/**
 * Send control packet via ring buffer
 *
 * @v vmdev             VMBus device
 * @v xid               Transaction ID (or zero to not request completion)
 * @v data              Data
 * @v len               Length of data
 * @ret rc              Return status code
 *
 * Send data using a VMBUS_DATA_INBAND packet.
 */
int vmbus_send_control ( struct vmbus_device *vmdev, uint64_t xid,
                         const void *data, size_t len ) {
        struct vmbus_packet_header *header = vmdev->packet;
 
        /* Construct header in packet buffer */
        assert ( header != NULL );
        header->type = cpu_to_le16 ( VMBUS_DATA_INBAND );
        header->hdr_qlen = cpu_to_le16 ( sizeof ( *header ) / 8 );
        header->flags = ( xid ?
                          cpu_to_le16 ( VMBUS_COMPLETION_REQUESTED ) : 0 );
        header->xid = xid; /* Non-endian */
 
        return vmbus_send ( vmdev, header, data, len );
}
 
/**
 * Send data packet via ring buffer
 *
 * @v vmdev             VMBus device
 * @v xid               Transaction ID
 * @v data              Data
 * @v len               Length of data
 * @v iobuf             I/O buffer
 * @ret rc              Return status code
 *
 * Send data using a VMBUS_DATA_GPA_DIRECT packet.  The caller is
 * responsible for ensuring that the I/O buffer remains untouched
 * until the corresponding completion has been received.
 */
int vmbus_send_data ( struct vmbus_device *vmdev, uint64_t xid,
                      const void *data, size_t len, struct io_buffer *iobuf ) {
        physaddr_t addr = virt_to_phys ( iobuf->data );
        unsigned int pfn_count = hv_pfn_count ( addr, iob_len ( iobuf ) );
        struct {
                struct vmbus_gpa_direct_header gpa;
                struct vmbus_gpa_range range;
                uint64_t pfn[pfn_count];
        } __attribute__ (( packed )) *header = vmdev->packet;
        unsigned int i;
 
        /* Sanity check */
        assert ( header != NULL );
        assert ( sizeof ( *header ) <= vmdev->mtu );
 
        /* Construct header in packet buffer */
        header->gpa.header.type = cpu_to_le16 ( VMBUS_DATA_GPA_DIRECT );
        header->gpa.header.hdr_qlen = cpu_to_le16 ( sizeof ( *header ) / 8 );
        header->gpa.header.flags = cpu_to_le16 ( VMBUS_COMPLETION_REQUESTED );
        header->gpa.header.xid = xid; /* Non-endian */
        header->gpa.range_count = 1;
        header->range.len = cpu_to_le32 ( iob_len ( iobuf ) );
        header->range.offset = cpu_to_le32 ( addr & ( PAGE_SIZE - 1 ) );
        for ( i = 0 ; i < pfn_count ; i++ )
                header->pfn[i] = ( ( addr / PAGE_SIZE ) + i );
 
        return vmbus_send ( vmdev, &header->gpa.header, data, len );
}
 
/**
 * Send completion packet via ring buffer
 *
 * @v vmdev             VMBus device
 * @v xid               Transaction ID
 * @v data              Data
 * @v len               Length of data
 * @ret rc              Return status code
 *
 * Send data using a VMBUS_COMPLETION packet.
 */
int vmbus_send_completion ( struct vmbus_device *vmdev, uint64_t xid,
                            const void *data, size_t len ) {
        struct vmbus_packet_header *header = vmdev->packet;
 
        /* Construct header in packet buffer */
        assert ( header != NULL );
        header->type = cpu_to_le16 ( VMBUS_COMPLETION );
        header->hdr_qlen = cpu_to_le16 ( sizeof ( *header ) / 8 );
        header->flags = 0;
        header->xid = xid; /* Non-endian */
 
        return vmbus_send ( vmdev, header, data, len );
}
 
/**
 * Send cancellation packet via ring buffer
 *
 * @v vmdev             VMBus device
 * @v xid               Transaction ID
 * @ret rc              Return status code
 *
 * Send data using a VMBUS_CANCELLATION packet.
 */
int vmbus_send_cancellation ( struct vmbus_device *vmdev, uint64_t xid ) {
        struct vmbus_packet_header *header = vmdev->packet;
 
        /* Construct header in packet buffer */
        assert ( header != NULL );
        header->type = cpu_to_le16 ( VMBUS_CANCELLATION );
        header->hdr_qlen = cpu_to_le16 ( sizeof ( *header ) / 8 );
        header->flags = 0;
        header->xid = xid; /* Non-endian */
 
        return vmbus_send ( vmdev, header, NULL, 0 );
}
 
/**
 * Get transfer page set from pageset ID
 *
 * @v vmdev             VMBus device
 * @v pageset           Page set ID (in protocol byte order)
 * @ret pages           Page set, or NULL if not found
 */
static struct vmbus_xfer_pages * vmbus_xfer_pages ( struct vmbus_device *vmdev,
                                                    uint16_t pageset ) {
        struct vmbus_xfer_pages *pages;
 
        /* Locate page set */
        list_for_each_entry ( pages, &vmdev->pages, list ) {
                if ( pages->pageset == pageset )
                        return pages;
        }
 
        DBGC ( vmdev, "VMBUS %s unrecognised page set ID %#04x\n",
               vmdev->dev.name, le16_to_cpu ( pageset ) );
        return NULL;
}
 
/**
 * Construct I/O buffer list from transfer pages
 *
 * @v vmdev             VMBus device
 * @v header            Transfer page header
 * @v list              I/O buffer list to populate
 * @ret rc              Return status code
 */
static int vmbus_xfer_page_iobufs ( struct vmbus_device *vmdev,
                                    struct vmbus_packet_header *header,
                                    struct list_head *list ) {
        struct vmbus_xfer_page_header *page_header =
                container_of ( header, struct vmbus_xfer_page_header, header );
        struct vmbus_xfer_pages *pages;
        struct io_buffer *iobuf;
        struct io_buffer *tmp;
        size_t len;
        size_t offset;
        unsigned int range_count;
        unsigned int i;
        int rc;
 
        /* Sanity check */
        assert ( header->type == cpu_to_le16 ( VMBUS_DATA_XFER_PAGES ) );
 
        /* Locate page set */
        pages = vmbus_xfer_pages ( vmdev, page_header->pageset );
        if ( ! pages ) {
                rc = -ENOENT;
                goto err_pages;
        }
 
        /* Allocate and populate I/O buffers */
        range_count = le32_to_cpu ( page_header->range_count );
        for ( i = 0 ; i < range_count ; i++ ) {
 
                /* Parse header */
                len = le32_to_cpu ( page_header->range[i].len );
                offset = le32_to_cpu ( page_header->range[i].offset );
 
                /* Allocate I/O buffer */
                iobuf = alloc_iob ( len );
                if ( ! iobuf ) {
                        DBGC ( vmdev, "VMBUS %s could not allocate %zd-byte "
                               "I/O buffer\n", vmdev->dev.name, len );
                        rc = -ENOMEM;
                        goto err_alloc;
                }
 
                /* Add I/O buffer to list */
                list_add ( &iobuf->list, list );
 
                /* Populate I/O buffer */
                if ( ( rc = pages->op->copy ( pages, iob_put ( iobuf, len ),
                                              offset, len ) ) != 0 ) {
                        DBGC ( vmdev, "VMBUS %s could not populate I/O buffer "
                               "range [%zd,%zd): %s\n",
                               vmdev->dev.name, offset, len, strerror ( rc ) );
                        goto err_copy;
                }
        }
 
        return 0;
 
 err_copy:
 err_alloc:
        list_for_each_entry_safe ( iobuf, tmp, list, list ) {
                list_del ( &iobuf->list );
                free_iob ( iobuf );
        }
 err_pages:
        return rc;
}
 
/**
 * Poll ring buffer
 *
 * @v vmdev             VMBus device
 * @ret rc              Return status code
 */
int vmbus_poll ( struct vmbus_device *vmdev ) {
        struct vmbus_packet_header *header = vmdev->packet;
        struct list_head list;
        void *data;
        size_t header_len;
        size_t len;
        size_t footer_len;
        size_t ring_len;
        size_t cons;
        size_t old_cons;
        uint64_t xid;
        int rc;
 
        /* Sanity checks */
        assert ( vmdev->packet != NULL );
        assert ( vmdev->in != NULL );
 
        /* Return immediately if buffer is empty */
        if ( ! vmbus_has_data ( vmdev ) )
                return 0;
        cons = le32_to_cpu ( vmdev->in->cons );
        old_cons = cons;
 
        /* Consume (start of) header */
        cons = vmbus_consume ( vmdev, cons, header, sizeof ( *header ) );
 
        /* Parse and sanity check header */
        header_len = ( le16_to_cpu ( header->hdr_qlen ) * 8 );
        if ( header_len < sizeof ( *header ) ) {
                DBGC ( vmdev, "VMBUS %s received underlength header (%zd "
                       "bytes)\n", vmdev->dev.name, header_len );
                return -EINVAL;
        }
        len = ( le16_to_cpu ( header->qlen ) * 8 );
        if ( len < header_len ) {
                DBGC ( vmdev, "VMBUS %s received underlength packet (%zd "
                       "bytes with %zd-byte header)\n",
                       vmdev->dev.name, len, header_len );
                return -EINVAL;
        }
        len -= header_len;
        footer_len = sizeof ( struct vmbus_packet_footer );
        ring_len = ( header_len + len + footer_len );
        if ( ring_len > vmdev->mtu ) {
                DBGC ( vmdev, "VMBUS %s received overlength packet (%zd "
                       "bytes)\n", vmdev->dev.name, ring_len );
                return -ERANGE;
        }
        xid = le64_to_cpu ( header->xid );
 
        /* Consume remainder of packet */
        cons = vmbus_consume ( vmdev, cons,
                               ( ( ( void * ) header ) + sizeof ( *header ) ),
                               ( ring_len - sizeof ( *header ) ) );
        DBGC2 ( vmdev, "VMBUS %s received:\n", vmdev->dev.name );
        DBGC2_HDA ( vmdev, old_cons, header, ring_len );
        assert ( ( ( cons - old_cons ) & ( vmdev->in_len - 1 ) ) == ring_len );
 
        /* Allocate I/O buffers, if applicable */
        INIT_LIST_HEAD ( &list );
        if ( header->type == cpu_to_le16 ( VMBUS_DATA_XFER_PAGES ) ) {
                if ( ( rc = vmbus_xfer_page_iobufs ( vmdev, header,
                                                     &list ) ) != 0 )
                        return rc;
        }
 
        /* Update producer index */
        rmb();
        vmdev->in->cons = cpu_to_le32 ( cons );
 
        /* Handle packet */
        data = ( ( ( void * ) header ) + header_len );
        switch ( header->type ) {
 
        case cpu_to_le16 ( VMBUS_DATA_INBAND ) :
                if ( ( rc = vmdev->op->recv_control ( vmdev, xid, data,
                                                      len ) ) != 0 ) {
                        DBGC ( vmdev, "VMBUS %s could not handle control "
                               "packet: %s\n",
                               vmdev->dev.name, strerror ( rc ) );
                        return rc;
                }
                break;
 
        case cpu_to_le16 ( VMBUS_DATA_XFER_PAGES ) :
                if ( ( rc = vmdev->op->recv_data ( vmdev, xid, data, len,
                                                   &list ) ) != 0 ) {
                        DBGC ( vmdev, "VMBUS %s could not handle data packet: "
                               "%s\n", vmdev->dev.name, strerror ( rc ) );
                        return rc;
                }
                break;
 
        case cpu_to_le16 ( VMBUS_COMPLETION ) :
                if ( ( rc = vmdev->op->recv_completion ( vmdev, xid, data,
                                                         len ) ) != 0 ) {
                        DBGC ( vmdev, "VMBUS %s could not handle completion: "
                               "%s\n", vmdev->dev.name, strerror ( rc ) );
                        return rc;
                }
                break;
 
        case cpu_to_le16 ( VMBUS_CANCELLATION ) :
                if ( ( rc = vmdev->op->recv_cancellation ( vmdev, xid ) ) != 0){
                        DBGC ( vmdev, "VMBUS %s could not handle cancellation: "
                               "%s\n", vmdev->dev.name, strerror ( rc ) );
                        return rc;
                }
                break;
 
        default:
                DBGC ( vmdev, "VMBUS %s unknown packet type %d\n",
                       vmdev->dev.name, le16_to_cpu ( header->type ) );
                return -ENOTSUP;
        }
 
        return 0;
}
 
/**
 * Dump channel status (for debugging)
 *
 * @v vmdev             VMBus device
 */
void vmbus_dump_channel ( struct vmbus_device *vmdev ) {
        size_t out_prod = le32_to_cpu ( vmdev->out->prod );
        size_t out_cons = le32_to_cpu ( vmdev->out->cons );
        size_t in_prod = le32_to_cpu ( vmdev->in->prod );
        size_t in_cons = le32_to_cpu ( vmdev->in->cons );
        size_t in_len;
        size_t first;
        size_t second;
 
        /* Dump ring status */
        DBGC ( vmdev, "VMBUS %s out %03zx:%03zx%s in %03zx:%03zx%s\n",
               vmdev->dev.name, out_prod, out_cons,
               ( vmdev->out->intr_mask ? "(m)" : "" ), in_prod, in_cons,
               ( vmdev->in->intr_mask ? "(m)" : "" ) );
 
        /* Dump inbound ring contents, if any */
        if ( in_prod != in_cons ) {
                in_len = ( ( in_prod - in_cons ) &
                           ( vmdev->in_len - 1 ) );
                first = ( vmdev->in_len - in_cons );
                if ( first > in_len )
                        first = in_len;
                second = ( in_len - first );
                DBGC_HDA ( vmdev, in_cons, &vmdev->in->data[in_cons], first );
                DBGC_HDA ( vmdev, 0, &vmdev->in->data[0], second );
        }
}
 
/**
 * Find driver for VMBus device
 *
 * @v vmdev             VMBus device
 * @ret driver          Driver, or NULL
 */
static struct vmbus_driver * vmbus_find_driver ( const union uuid *type ) {
        struct vmbus_driver *vmdrv;
 
        for_each_table_entry ( vmdrv, VMBUS_DRIVERS ) {
                if ( memcmp ( &vmdrv->type, type, sizeof ( *type ) ) == 0 )
                        return vmdrv;
        }
        return NULL;
}
 
/**
 * Probe channels
 *
 * @v hv                Hyper-V hypervisor
 * @v parent            Parent device
 * @ret rc              Return status code
 */
static int vmbus_probe_channels ( struct hv_hypervisor *hv,
                                  struct device *parent ) {
        struct vmbus *vmbus = hv->vmbus;
        const struct vmbus_message_header *header = &vmbus->message->header;
        const struct vmbus_offer_channel *offer = &vmbus->message->offer;
        const union uuid *type;
        union uuid instance;
        struct vmbus_driver *driver;
        struct vmbus_device *vmdev;
        struct vmbus_device *tmp;
        unsigned int channel;
        int rc;
 
        /* Post message */
        if ( ( rc = vmbus_post_empty_message ( hv, VMBUS_REQUEST_OFFERS ) ) !=0)
                goto err_post_message;
 
        /* Collect responses */
        while ( 1 ) {
 
                /* Wait for response */
                if ( ( rc = vmbus_wait_for_any_message ( hv ) ) != 0 )
                        goto err_wait_for_any_message;
 
                /* Handle response */
                if ( header->type == cpu_to_le32 ( VMBUS_OFFER_CHANNEL ) ) {
 
                        /* Parse offer */
                        type = &offer->type;
                        channel = le32_to_cpu ( offer->channel );
                        DBGC2 ( vmbus, "VMBUS %p offer %d type %s",
                                vmbus, channel, uuid_ntoa ( type ) );
                        if ( offer->monitored )
                                DBGC2 ( vmbus, " monitor %d", offer->monitor );
                        DBGC2 ( vmbus, "\n" );
 
                        /* Look for a driver */
                        driver = vmbus_find_driver ( type );
                        if ( ! driver ) {
                                DBGC2 ( vmbus, "VMBUS %p has no driver for "
                                        "type %s\n", vmbus, uuid_ntoa ( type ));
                                /* Not a fatal error */
                                continue;
                        }
 
                        /* Allocate and initialise device */
                        vmdev = zalloc ( sizeof ( *vmdev ) );
                        if ( ! vmdev ) {
                                rc = -ENOMEM;
                                goto err_alloc_vmdev;
                        }
                        memcpy ( &instance, &offer->instance,
                                 sizeof ( instance ) );
                        uuid_mangle ( &instance );
                        snprintf ( vmdev->dev.name, sizeof ( vmdev->dev.name ),
                                   "{%s}", uuid_ntoa ( &instance ) );
                        vmdev->dev.desc.bus_type = BUS_TYPE_HV;
                        INIT_LIST_HEAD ( &vmdev->dev.children );
                        list_add_tail ( &vmdev->dev.siblings,
                                        &parent->children );
                        vmdev->dev.parent = parent;
                        vmdev->hv = hv;
                        memcpy ( &vmdev->instance, &offer->instance,
                                 sizeof ( vmdev->instance ) );
                        vmdev->channel = channel;
                        vmdev->monitor = offer->monitor;
                        vmdev->signal = ( offer->monitored ?
                                          vmbus_signal_monitor :
                                          vmbus_signal_event );
                        INIT_LIST_HEAD ( &vmdev->pages );
                        vmdev->driver = driver;
                        vmdev->dev.driver_name = driver->name;
                        DBGC ( vmdev, "VMBUS %s has driver \"%s\"\n",
                               vmdev->dev.name, vmdev->driver->name );
 
                } else if ( header->type ==
                            cpu_to_le32 ( VMBUS_ALL_OFFERS_DELIVERED ) ) {
 
                        /* End of offer list */
                        break;
 
                } else {
                        DBGC ( vmbus, "VMBUS %p unexpected offer response type "
                               "%d\n", vmbus, le32_to_cpu ( header->type ) );
                        rc = -EPROTO;
                        goto err_unexpected_offer;
                }
        }
 
        /* Probe all devices.  We do this only after completing
         * enumeration since devices will need to send and receive
         * VMBus messages.
         */
        list_for_each_entry ( vmdev, &parent->children, dev.siblings ) {
                if ( ( rc = vmdev->driver->probe ( vmdev ) ) != 0 ) {
                        DBGC ( vmdev, "VMBUS %s could not probe: %s\n",
                               vmdev->dev.name, strerror ( rc ) );
                        goto err_probe;
                }
        }
 
        return 0;
 
 err_probe:
        /* Remove driver from each device that was already probed */
        list_for_each_entry_continue_reverse ( vmdev, &parent->children,
                                               dev.siblings ) {
                vmdev->driver->remove ( vmdev );
        }
 err_unexpected_offer:
 err_alloc_vmdev:
 err_wait_for_any_message:
        /* Free any devices allocated (but potentially not yet probed) */
        list_for_each_entry_safe ( vmdev, tmp, &parent->children,
                                   dev.siblings ) {
                list_del ( &vmdev->dev.siblings );
                free ( vmdev );
        }
 err_post_message:
        return rc;
}
 
 
/**
 * Reset channels
 *
 * @v hv                Hyper-V hypervisor
 * @v parent            Parent device
 * @ret rc              Return status code
 */
static int vmbus_reset_channels ( struct hv_hypervisor *hv,
                                  struct device *parent ) {
        struct vmbus *vmbus = hv->vmbus;
        const struct vmbus_message_header *header = &vmbus->message->header;
        const struct vmbus_offer_channel *offer = &vmbus->message->offer;
        const union uuid *type;
        struct vmbus_device *vmdev;
        unsigned int channel;
        int rc;
 
        /* Post message */
        if ( ( rc = vmbus_post_empty_message ( hv, VMBUS_REQUEST_OFFERS ) ) !=0)
                return rc;
 
        /* Collect responses */
        while ( 1 ) {
 
                /* Wait for response */
                if ( ( rc = vmbus_wait_for_any_message ( hv ) ) != 0 )
                        return rc;
 
                /* Handle response */
                if ( header->type == cpu_to_le32 ( VMBUS_OFFER_CHANNEL ) ) {
 
                        /* Parse offer */
                        type = &offer->type;
                        channel = le32_to_cpu ( offer->channel );
                        DBGC2 ( vmbus, "VMBUS %p offer %d type %s",
                                vmbus, channel, uuid_ntoa ( type ) );
                        if ( offer->monitored )
                                DBGC2 ( vmbus, " monitor %d", offer->monitor );
                        DBGC2 ( vmbus, "\n" );
 
                        /* Do nothing with the offer; we already have all
                         * of the relevant state from the initial probe.
                         */
 
                } else if ( header->type ==
                            cpu_to_le32 ( VMBUS_ALL_OFFERS_DELIVERED ) ) {
 
                        /* End of offer list */
                        break;
 
                } else {
                        DBGC ( vmbus, "VMBUS %p unexpected offer response type "
                               "%d\n", vmbus, le32_to_cpu ( header->type ) );
                        return -EPROTO;
                }
        }
 
        /* Reset all devices */
        list_for_each_entry ( vmdev, &parent->children, dev.siblings ) {
                if ( ( rc = vmdev->driver->reset ( vmdev ) ) != 0 ) {
                        DBGC ( vmdev, "VMBUS %s could not reset: %s\n",
                               vmdev->dev.name, strerror ( rc ) );
                        /* Continue attempting to reset other devices */
                        continue;
                }
        }
 
        return 0;
}
 
/**
 * Remove channels
 *
 * @v hv                Hyper-V hypervisor
 * @v parent            Parent device
 */
static void vmbus_remove_channels ( struct hv_hypervisor *hv __unused,
                                    struct device *parent ) {
        struct vmbus_device *vmdev;
        struct vmbus_device *tmp;
 
        /* Remove devices */
        list_for_each_entry_safe ( vmdev, tmp, &parent->children,
                                   dev.siblings ) {
                vmdev->driver->remove ( vmdev );
                assert ( list_empty ( &vmdev->dev.children ) );
                assert ( vmdev->out == NULL );
                assert ( vmdev->in == NULL );
                assert ( vmdev->packet == NULL );
                assert ( list_empty ( &vmdev->pages ) );
                list_del ( &vmdev->dev.siblings );
                free ( vmdev );
        }
}
 
/**
 * Probe Hyper-V virtual machine bus
 *
 * @v hv                Hyper-V hypervisor
 * @v parent            Parent device
 * @ret rc              Return status code
 */
int vmbus_probe ( struct hv_hypervisor *hv, struct device *parent ) {
        struct vmbus *vmbus;
        int rc;
 
        /* Allocate and initialise structure */
        vmbus = zalloc ( sizeof ( *vmbus ) );
        if ( ! vmbus ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        hv->vmbus = vmbus;
 
        /* Initialise message buffer pointer
         *
         * We use a pointer to the fixed-size Hyper-V received message
         * buffer.  This allows us to access fields within received
         * messages without first checking the message size: any
         * fields beyond the end of the message will read as zero.
         */
        vmbus->message = ( ( void * ) hv->message->received.data );
        assert ( sizeof ( *vmbus->message ) <=
                 sizeof ( hv->message->received.data ) );
 
        /* Allocate interrupt and monitor pages */
        if ( ( rc = hv_alloc_pages ( hv, &vmbus->intr, &vmbus->monitor_in,
                                     &vmbus->monitor_out, NULL ) ) != 0 )
                goto err_alloc_pages;
 
        /* Enable message interrupt */
        hv_enable_sint ( hv, VMBUS_MESSAGE_SINT );
 
        /* Negotiate protocol version */
        if ( ( rc = vmbus_negotiate_version ( hv ) ) != 0 )
                goto err_negotiate_version;
 
        /* Enumerate channels */
        if ( ( rc = vmbus_probe_channels ( hv, parent ) ) != 0 )
                goto err_probe_channels;
 
        return 0;
 
        vmbus_remove_channels ( hv, parent );
 err_probe_channels:
        vmbus_unload ( hv );
 err_negotiate_version:
        hv_disable_sint ( hv, VMBUS_MESSAGE_SINT );
        hv_free_pages ( hv, vmbus->intr, vmbus->monitor_in, vmbus->monitor_out,
                        NULL );
 err_alloc_pages:
        free ( vmbus );
 err_alloc:
        return rc;
}
 
/**
 * Reset Hyper-V virtual machine bus
 *
 * @v hv                Hyper-V hypervisor
 * @v parent            Parent device
 * @ret rc              Return status code
 */
int vmbus_reset ( struct hv_hypervisor *hv, struct device *parent ) {
        struct vmbus *vmbus = hv->vmbus;
        int rc;
 
        /* Mark all existent GPADLs as obsolete */
        vmbus_obsolete_gpadl = vmbus_gpadl;
 
        /* Clear interrupt and monitor pages */
        memset ( vmbus->intr, 0, PAGE_SIZE );
        memset ( vmbus->monitor_in, 0, PAGE_SIZE );
        memset ( vmbus->monitor_out, 0, PAGE_SIZE );
 
        /* Enable message interrupt */
        hv_enable_sint ( hv, VMBUS_MESSAGE_SINT );
 
        /* Renegotiate protocol version */
        if ( ( rc = vmbus_negotiate_version ( hv ) ) != 0 )
                return rc;
 
        /* Reenumerate channels */
        if ( ( rc = vmbus_reset_channels ( hv, parent ) ) != 0 )
                return rc;
 
        return 0;
}
 
/**
 * Remove Hyper-V virtual machine bus
 *
 * @v hv                Hyper-V hypervisor
 * @v parent            Parent device
 */
void vmbus_remove ( struct hv_hypervisor *hv, struct device *parent ) {
        struct vmbus *vmbus = hv->vmbus;
 
        vmbus_remove_channels ( hv, parent );
        vmbus_unload ( hv );
        hv_disable_sint ( hv, VMBUS_MESSAGE_SINT );
        hv_free_pages ( hv, vmbus->intr, vmbus->monitor_in, vmbus->monitor_out,
                        NULL );
        free ( vmbus );
}