netfront.h

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#ifndef _NETFRONT_H
#define _NETFRONT_H

/** @file
 *
 * Xen netfront driver
 *
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );

#include <ipxe/xen.h>
#include <xen/io/netif.h>

/** Number of transmit ring entries */
#define NETFRONT_NUM_TX_DESC 16

/** Number of receive ring entries */
#define NETFRONT_NUM_RX_DESC 32

/** Receive ring fill level
 *
 * The xen-netback driver from kernels 3.18 to 4.2 inclusive have a
 * bug (CA-163395) which prevents packet reception if fewer than 18
 * receive descriptors are available.  This was fixed in upstream
 * kernel commit d5d4852 ("xen-netback: require fewer guest Rx slots
 * when not using GSO").
 *
 * We provide 18 receive descriptors to avoid unpleasant silent
 * failures on these kernel versions.
 */
#define NETFRONT_RX_FILL 18

/** Grant reference indices */
enum netfront_ref_index {
        /** Transmit ring grant reference index */
        NETFRONT_REF_TX_RING = 0,
        /** Transmit descriptor grant reference base index */
        NETFRONT_REF_TX_BASE,
        /** Receive ring grant reference index */
        NETFRONT_REF_RX_RING = ( NETFRONT_REF_TX_BASE + NETFRONT_NUM_TX_DESC ),
        /** Receive descriptor grant reference base index */
        NETFRONT_REF_RX_BASE,
        /** Total number of grant references required */
        NETFRONT_REF_COUNT = ( NETFRONT_REF_RX_BASE + NETFRONT_NUM_RX_DESC )
};

/** A netfront descriptor ring */
struct netfront_ring {
        /** Shared ring */
        union {
                /** Transmit shared ring */
                netif_tx_sring_t *tx;
                /** Receive shared ring */
                netif_rx_sring_t *rx;
                /** Raw pointer */
                void *raw;
        } sring;
        /** Shared ring grant reference key */
        const char *ref_key;
        /** Shared ring grant reference */
        grant_ref_t ref;

        /** Maximum number of used descriptors */
        size_t count;
        /** I/O buffers, indexed by buffer ID */
        struct io_buffer **iobufs;
        /** Grant references, indexed by buffer ID */
        grant_ref_t *refs;

        /** Buffer ID ring */
        uint8_t *ids;
        /** Buffer ID ring producer counter */
        unsigned int id_prod;
        /** Buffer ID ring consumer counter */
        unsigned int id_cons;
};

/**
 * Initialise descriptor ring
 *
 * @v ring              Descriptor ring
 * @v ref_key           Shared ring grant reference key
 * @v ref               Shared ring grant reference
 * @v count             Maxium number of used descriptors
 * @v iobufs            I/O buffers
 * @v refs              I/O buffer grant references
 * @v ids               Buffer IDs
 */
static inline __attribute__ (( always_inline )) void
netfront_init_ring ( struct netfront_ring *ring, const char *ref_key,
                     grant_ref_t ref, unsigned int count,
                     struct io_buffer **iobufs, grant_ref_t *refs,
                     uint8_t *ids ) {

        ring->ref_key = ref_key;
        ring->ref = ref;
        ring->count = count;
        ring->iobufs = iobufs;
        ring->refs = refs;
        ring->ids = ids;
}

/**
 * Calculate descriptor ring fill level
 *
 * @v ring              Descriptor ring
 * @v fill              Fill level
 */
static inline __attribute__ (( always_inline )) unsigned int
netfront_ring_fill ( struct netfront_ring *ring ) {
        unsigned int fill_level;

        fill_level = ( ring->id_prod - ring->id_cons );
        assert ( fill_level <= ring->count );
        return fill_level;
}

/**
 * Calculate descriptor ring remaining space
 *
 * @v ring              Descriptor ring
 * @v space             Number of unused entries
 */
static inline __attribute__ (( always_inline )) unsigned int
netfront_ring_space ( struct netfront_ring *ring ) {

        return ( ring->count - netfront_ring_fill ( ring ) );
}

/**
 * Check whether or not descriptor ring is full
 *
 * @v ring              Descriptor ring
 * @v is_full           Ring is full
 */
static inline __attribute__ (( always_inline )) int
netfront_ring_is_full ( struct netfront_ring *ring ) {

        return ( netfront_ring_fill ( ring ) >= ring->count );
}

/**
 * Check whether or not descriptor ring is empty
 *
 * @v ring              Descriptor ring
 * @v is_empty          Ring is empty
 */
static inline __attribute__ (( always_inline )) int
netfront_ring_is_empty ( struct netfront_ring *ring ) {

        return ( netfront_ring_fill ( ring ) == 0 );
}

/** A netfront NIC */
struct netfront_nic {
        /** Xen device */
        struct xen_device *xendev;
        /** Grant references */
        grant_ref_t refs[NETFRONT_REF_COUNT];

        /** Network device */
        struct net_device *netdev;
        /** List of netfront NICs */
        struct list_head list;

        /** Transmit ring */
        struct netfront_ring tx;
        /** Transmit front ring */
        netif_tx_front_ring_t tx_fring;
        /** Transmit I/O buffers */
        struct io_buffer *tx_iobufs[NETFRONT_NUM_TX_DESC];
        /** Transmit I/O buffer IDs */
        uint8_t tx_ids[NETFRONT_NUM_TX_DESC];

        /** Receive ring */
        struct netfront_ring rx;
        /** Receive front ring */
        netif_rx_front_ring_t rx_fring;
        /** Receive I/O buffers */
        struct io_buffer *rx_iobufs[NETFRONT_NUM_RX_DESC];
        /** Receive I/O buffer IDs */
        uint8_t rx_ids[NETFRONT_NUM_RX_DESC];
        /** Partial receive I/O buffer list */
        struct list_head rx_partial;

        /** Event channel */
        struct evtchn_send event;
};

/** Transmit shared ring field */
#define tx_sring tx.sring.tx

/** Receive shared ring field */
#define rx_sring rx.sring.rx

#endif /* _NETFRONT_H */