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_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_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;
	if (src->operation == BLKIF_OP_DISCARD) {
		struct blkif_request_discard *s = (void *)src;
		struct blkif_request_discard *d = (void *)dst;
		d->nr_sectors = s->nr_sectors;
		return;
	}
	/* prevent the compiler from optimizing the code and using src->nr_segments instead */
	barrier();
	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;
	if (src->operation == BLKIF_OP_DISCARD) {
		struct blkif_request_discard *s = (void *)src;
		struct blkif_request_discard *d = (void *)dst;
		d->nr_sectors = s->nr_sectors;
		return;
	}
	/* prevent the compiler from optimizing the code and using src->nr_segments instead */
	barrier();
	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__ */