pcimsix.c

Go to the documentation of this file.

/*
 * Copyright (C) 2019 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 );

#include <stdint.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/pci.h>
#include <ipxe/pcimsix.h>

/** @file
 *
 * PCI MSI-X interrupts
 *
 * Interrupts as such are not used in iPXE, which operates in polling
 * mode.  However, some network cards (such as the Intel 40GbE and
 * 100GbE NICs) will defer writing out completions until the point of
 * asserting an MSI-X interrupt.
 *
 * From the point of view of the PCI device, asserting an MSI-X
 * interrupt is just a 32-bit DMA write of an opaque value to an
 * opaque target address.  The PCI device has no know to know whether
 * or not the target address corresponds to a real APIC.
 *
 * We can therefore trick the PCI device into believing that it is
 * asserting an MSI-X interrupt, by configuring it to write an opaque
 * 32-bit value to a dummy target address in host memory.  This is
 * sufficient to trigger the associated write of the completions to
 * host memory.
 *
 * When running in a virtual machine, the hypervisor will intercept
 * our attempt to configure MSI-X on the PCI device.  The physical
 * hardware will be configured to raise an interrupt under the
 * hypervisor's control, which will then be reflected back into the
 * virtual machine.  The opaque value that we write will be assumed to
 * indicate an interrupt vector number (as would normally be the case
 * when configuring MSI-X), and the opaque address will generally be
 * ignored.  The reflected interrupt will be ignored (since it is not
 * enabled within the virtual machine), but the device still asserts
 * an MSI-X interrupt and so still triggers the associated write of
 * the completions to host memory.
 *
 * Note that since the opaque target address will generally be ignored
 * by the hypervisor, we cannot examine the value present at the dummy
 * target address to find out whether or not an interrupt has been
 * raised.
 */

/**
 * Get MSI-X descriptor name (for debugging)
 *
 * @v cfg               Configuration space offset
 * @ret name            Descriptor name
 */
static const char * pci_msix_name ( unsigned int cfg ) {

        switch ( cfg ) {
        case PCI_MSIX_DESC_TABLE:       return "table";
        case PCI_MSIX_DESC_PBA:         return "PBA";
        default:                        return "<UNKNOWN>";
        }
}

/**
 * Map MSI-X BAR portion
 *
 * @v pci               PCI device
 * @v msix              MSI-X capability
 * @v cfg               Configuration space offset
 * @ret io              I/O address
 */
static void * pci_msix_ioremap ( struct pci_device *pci, struct pci_msix *msix,
                                 unsigned int cfg ) {
        uint32_t desc;
        unsigned int bar;
        unsigned long start;
        unsigned long offset;
        unsigned long base;
        void *io;

        /* Read descriptor */
        pci_read_config_dword ( pci, ( msix->cap + cfg ), &desc );

        /* Get BAR */
        bar = PCI_MSIX_DESC_BIR ( desc );
        offset = PCI_MSIX_DESC_OFFSET ( desc );
        start = pci_bar_start ( pci, PCI_BASE_ADDRESS ( bar ) );
        if ( ! start ) {
                DBGC ( msix, "MSI-X %p %s could not find BAR%d\n",
                       msix, pci_msix_name ( cfg ), bar );
                return NULL;
        }
        base = ( start + offset );
        DBGC ( msix, "MSI-X %p %s at %#08lx (BAR%d+%#lx)\n",
               msix, pci_msix_name ( cfg ), base, bar, offset );

        /* Map BAR portion */
        io = pci_ioremap ( pci, ( start + offset ), PCI_MSIX_LEN );
        if ( ! io ) {
                DBGC ( msix, "MSI-X %p %s could not map %#08lx\n",
                       msix, pci_msix_name ( cfg ), base );
                return NULL;
        }

        return io;
}

/**
 * Enable MSI-X interrupts
 *
 * @v pci               PCI device
 * @v msix              MSI-X capability
 * @ret rc              Return status code
 */
int pci_msix_enable ( struct pci_device *pci, struct pci_msix *msix ) {
        uint16_t ctrl;
        physaddr_t msg;
        unsigned int i;
        int rc;

        /* Locate capability */
        msix->cap = pci_find_capability ( pci, PCI_CAP_ID_MSIX );
        if ( ! msix->cap ) {
                DBGC ( msix, "MSI-X %p found no MSI-X capability in "
                       PCI_FMT "\n", msix, PCI_ARGS ( pci ) );
                rc = -ENOENT;
                goto err_cap;
        }

        /* Extract interrupt count */
        pci_read_config_word ( pci, ( msix->cap + PCI_MSIX_CTRL ), &ctrl );
        msix->count = ( PCI_MSIX_CTRL_SIZE ( ctrl ) + 1 );
        DBGC ( msix, "MSI-X %p has %d vectors for " PCI_FMT "\n",
               msix, msix->count, PCI_ARGS ( pci ) );

        /* Map MSI-X table */
        msix->table = pci_msix_ioremap ( pci, msix, PCI_MSIX_DESC_TABLE );
        if ( ! msix->table ) {
                rc = -ENOENT;
                goto err_table;
        }

        /* Map pending bit array */
        msix->pba = pci_msix_ioremap ( pci, msix, PCI_MSIX_DESC_PBA );
        if ( ! msix->pba ) {
                rc = -ENOENT;
                goto err_pba;
        }

        /* Allocate dummy target */
        msix->msg = dma_alloc ( &pci->dma, &msix->map, sizeof ( *msix->msg ),
                                sizeof ( *msix->msg ) );
        if ( ! msix->msg ) {
                rc = -ENOMEM;
                goto err_msg;
        }

        /* Map all interrupts to dummy target by default */
        msg = dma ( &msix->map, msix->msg );
        for ( i = 0 ; i < msix->count ; i++ )
                pci_msix_map ( msix, i, msg, 0 );

        /* Enable MSI-X */
        ctrl &= ~PCI_MSIX_CTRL_MASK;
        ctrl |= PCI_MSIX_CTRL_ENABLE;
        pci_write_config_word ( pci, ( msix->cap + PCI_MSIX_CTRL ), ctrl );

        return 0;

        dma_free ( &msix->map, msix->msg, sizeof ( *msix->msg ) );
 err_msg:
        iounmap ( msix->pba );
 err_pba:
        iounmap ( msix->table );
 err_table:
 err_cap:
        return rc;
}

/**
 * Disable MSI-X interrupts
 *
 * @v pci               PCI device
 * @v msix              MSI-X capability
 */
void pci_msix_disable ( struct pci_device *pci, struct pci_msix *msix ) {
        uint16_t ctrl;

        /* Disable MSI-X */
        pci_read_config_word ( pci, ( msix->cap + PCI_MSIX_CTRL ), &ctrl );
        ctrl &= ~PCI_MSIX_CTRL_ENABLE;
        pci_write_config_word ( pci, ( msix->cap + PCI_MSIX_CTRL ), ctrl );

        /* Free dummy target */
        dma_free ( &msix->map, msix->msg, sizeof ( *msix->msg ) );

        /* Unmap pending bit array */
        iounmap ( msix->pba );

        /* Unmap MSI-X table */
        iounmap ( msix->table );
}

/**
 * Map MSI-X interrupt vector
 *
 * @v msix              MSI-X capability
 * @v vector            MSI-X vector
 * @v address           Message address
 * @v data              Message data
 */
void pci_msix_map ( struct pci_msix *msix, unsigned int vector,
                    physaddr_t address, uint32_t data ) {
        void *base;

        /* Sanity check */
        assert ( vector < msix->count );

        /* Map interrupt vector */
        base = ( msix->table + PCI_MSIX_VECTOR ( vector ) );
        writel ( ( address & 0xffffffffUL ), ( base + PCI_MSIX_ADDRESS_LO ) );
        if ( sizeof ( address ) > sizeof ( uint32_t ) ) {
                writel ( ( ( ( uint64_t ) address ) >> 32 ),
                         ( base + PCI_MSIX_ADDRESS_HI ) );
        } else {
                writel ( 0, ( base + PCI_MSIX_ADDRESS_HI ) );
        }
        writel ( data, ( base + PCI_MSIX_DATA ) );
}

/**
 * Control MSI-X interrupt vector
 *
 * @v msix              MSI-X capability
 * @v vector            MSI-X vector
 * @v mask              Control mask
 */
void pci_msix_control ( struct pci_msix *msix, unsigned int vector,
                        uint32_t mask ) {
        void *base;
        uint32_t ctrl;

        /* Mask/unmask interrupt vector */
        base = ( msix->table + PCI_MSIX_VECTOR ( vector ) );
        ctrl = readl ( base + PCI_MSIX_CONTROL );
        ctrl &= ~PCI_MSIX_CONTROL_MASK;
        ctrl |= mask;
        writel ( ctrl, ( base + PCI_MSIX_CONTROL ) );
}

/**
 * Dump MSI-X interrupt state (for debugging)
 *
 * @v msix              MSI-X capability
 * @v vector            MSI-X vector
 */
void pci_msix_dump ( struct pci_msix *msix, unsigned int vector ) {
        void *base;
        uint32_t address_hi;
        uint32_t address_lo;
        physaddr_t address;
        uint32_t data;
        uint32_t ctrl;
        uint32_t pba;

        /* Do nothing in non-debug builds */
        if ( ! DBG_LOG )
                return;

        /* Mask/unmask interrupt vector */
        base = ( msix->table + PCI_MSIX_VECTOR ( vector ) );
        address_hi = readl ( base + PCI_MSIX_ADDRESS_HI );
        address_lo = readl ( base + PCI_MSIX_ADDRESS_LO );
        data = readl ( base + PCI_MSIX_DATA );
        ctrl = readl ( base + PCI_MSIX_CONTROL );
        pba = readl ( msix->pba );
        address = ( ( ( ( uint64_t ) address_hi ) << 32 ) | address_lo );
        DBGC ( msix, "MSI-X %p vector %d %#08x => %#08lx%s%s\n",
               msix, vector, data, address,
               ( ( ctrl & PCI_MSIX_CONTROL_MASK ) ? " (masked)" : "" ),
               ( ( pba & ( 1 << vector ) ) ? " (pending)" : "" ) );
}