qemu/hw/block/xen_blkif.h

#ifndef XEN_BLKIF_H
#define XEN_BLKIF_H

#include <xen/io/ring.h>
#include <xen/io/blkif.h>
#include <xen/io/protocols.h>

/*
 * Not a real protocol.  Used to generate ring structs which contain
 * the elements common to all protocols only.  This way we get a
 * compiler-checkable way to use common struct elements, so we can
 * avoid using switch(protocol) in a number of places.
 */
struct blkif_common_request {
    char dummy;
};
struct blkif_common_response {
    char dummy;
};

/* i386 protocol version */
#pragma pack(push, 4)
struct blkif_x86_32_request {
    uint8_t        operation;        /* BLKIF_OP_???                         */
    uint8_t        nr_segments;      /* number of segments                   */
    blkif_vdev_t   handle;           /* only for read/write requests         */
    uint64_t       id;               /* private guest value, echoed in resp  */
    blkif_sector_t sector_number;    /* start sector idx on disk (r/w only)  */
    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
};
struct blkif_x86_32_request_discard {
    uint8_t        operation;        /* BLKIF_OP_DISCARD                     */
    uint8_t        flag;             /* nr_segments in request struct        */
    blkif_vdev_t   handle;           /* only for read/write requests         */
    uint64_t       id;               /* private guest value, echoed in resp  */
    blkif_sector_t sector_number;    /* start sector idx on disk (r/w only)  */
    uint64_t       nr_sectors;       /* # of contiguous sectors to discard   */
};
struct blkif_x86_32_response {
    uint64_t        id;              /* copied from request */
    uint8_t         operation;       /* copied from request */
    int16_t         status;          /* BLKIF_RSP_???       */
};
typedef struct blkif_x86_32_request blkif_x86_32_request_t;
typedef struct blkif_x86_32_response blkif_x86_32_response_t;
#pragma pack(pop)

/* x86_64 protocol version */
struct blkif_x86_64_request {
    uint8_t        operation;        /* BLKIF_OP_???                         */
    uint8_t        nr_segments;      /* number of segments                   */
    blkif_vdev_t   handle;           /* only for read/write requests         */
    uint64_t       __attribute__((__aligned__(8))) id;
    blkif_sector_t sector_number;    /* start sector idx on disk (r/w only)  */
    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
};
struct blkif_x86_64_request_discard {
    uint8_t        operation;        /* BLKIF_OP_DISCARD                     */
    uint8_t        flag;             /* nr_segments in request struct        */
    blkif_vdev_t   handle;           /* only for read/write requests         */
    uint64_t       __attribute__((__aligned__(8))) id;
    blkif_sector_t sector_number;    /* start sector idx on disk (r/w only)  */
    uint64_t       nr_sectors;       /* # of contiguous sectors to discard   */
};
struct blkif_x86_64_response {
    uint64_t       __attribute__((__aligned__(8))) id;
    uint8_t         operation;       /* copied from request */
    int16_t         status;          /* BLKIF_RSP_???       */
};
typedef struct blkif_x86_64_request blkif_x86_64_request_t;
typedef struct blkif_x86_64_response blkif_x86_64_response_t;

DEFINE_RING_TYPES(blkif_common, struct blkif_common_request,
                  struct blkif_common_response);
DEFINE_RING_TYPES(blkif_x86_32, struct blkif_x86_32_request,
                  struct blkif_x86_32_response);
DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request,
                  struct blkif_x86_64_response);

union blkif_back_rings {
    blkif_back_ring_t        native;
    blkif_common_back_ring_t common;
    blkif_x86_32_back_ring_t x86_32_part;
    blkif_x86_64_back_ring_t x86_64_part;
};
typedef union blkif_back_rings blkif_back_rings_t;

enum blkif_protocol {
    BLKIF_PROTOCOL_NATIVE = 1,
    BLKIF_PROTOCOL_X86_32 = 2,
    BLKIF_PROTOCOL_X86_64 = 3,
};

static inline void blkif_get_x86_32_req(blkif_request_t *dst,
                                        blkif_x86_32_request_t *src)
{
    int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;

    dst->operation = src->operation;
    dst->nr_segments = src->nr_segments;
    dst->handle = src->handle;
    dst->id = src->id;
    dst->sector_number = src->sector_number;
    /* Prevent the compiler from using src->... instead. */
    barrier();
    if (dst->operation == BLKIF_OP_DISCARD) {
        struct blkif_x86_32_request_discard *s = (void *)src;
        struct blkif_request_discard *d = (void *)dst;
        d->nr_sectors = s->nr_sectors;
        return;
    }
    if (n > dst->nr_segments) {
        n = dst->nr_segments;
    }
    for (i = 0; i < n; i++) {
        dst->seg[i] = src->seg[i];
    }
}

static inline void blkif_get_x86_64_req(blkif_request_t *dst,
                                        blkif_x86_64_request_t *src)
{
    int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;

    dst->operation = src->operation;
    dst->nr_segments = src->nr_segments;
    dst->handle = src->handle;
    dst->id = src->id;
    dst->sector_number = src->sector_number;
    /* Prevent the compiler from using src->... instead. */
    barrier();
    if (dst->operation == BLKIF_OP_DISCARD) {
        struct blkif_x86_64_request_discard *s = (void *)src;
        struct blkif_request_discard *d = (void *)dst;
        d->nr_sectors = s->nr_sectors;
        return;
    }
    if (n > dst->nr_segments) {
        n = dst->nr_segments;
    }
    for (i = 0; i < n; i++) {
        dst->seg[i] = src->seg[i];
    }
}

#endif /* XEN_BLKIF_H */