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qemu-e2k/block/vpc.c
Zhang Shengju c088b69136 block/vpc: write checksum back to footer after check 
After validation check, the 'checksum' is not written back
to footer, which leave it with zero.

This results in errors while loadding it under Microsoft's
Hyper-V environment, and also errors from utilities like
Citrix's vhd-util.

Signed-off-by: Zhang Shengju <sean_zhang@trendmicro.com.cn>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-05 14:54:40 +02:00

800 lines
22 KiB
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/*
* Block driver for Connectix / Microsoft Virtual PC images
*
* Copyright (c) 2005 Alex Beregszaszi
* Copyright (c) 2009 Kevin Wolf <kwolf@suse.de>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "block_int.h"
#include "module.h"
#include "migration.h"
/**************************************************************/
#define HEADER_SIZE 512
//#define CACHE
enum vhd_type {
VHD_FIXED = 2,
VHD_DYNAMIC = 3,
VHD_DIFFERENCING = 4,
};
// Seconds since Jan 1, 2000 0:00:00 (UTC)
#define VHD_TIMESTAMP_BASE 946684800
// always big-endian
struct vhd_footer {
char creator[8]; // "conectix"
uint32_t features;
uint32_t version;
// Offset of next header structure, 0xFFFFFFFF if none
uint64_t data_offset;
// Seconds since Jan 1, 2000 0:00:00 (UTC)
uint32_t timestamp;
char creator_app[4]; // "vpc "
uint16_t major;
uint16_t minor;
char creator_os[4]; // "Wi2k"
uint64_t orig_size;
uint64_t size;
uint16_t cyls;
uint8_t heads;
uint8_t secs_per_cyl;
uint32_t type;
// Checksum of the Hard Disk Footer ("one's complement of the sum of all
// the bytes in the footer without the checksum field")
uint32_t checksum;
// UUID used to identify a parent hard disk (backing file)
uint8_t uuid[16];
uint8_t in_saved_state;
};
struct vhd_dyndisk_header {
char magic[8]; // "cxsparse"
// Offset of next header structure, 0xFFFFFFFF if none
uint64_t data_offset;
// Offset of the Block Allocation Table (BAT)
uint64_t table_offset;
uint32_t version;
uint32_t max_table_entries; // 32bit/entry
// 2 MB by default, must be a power of two
uint32_t block_size;
uint32_t checksum;
uint8_t parent_uuid[16];
uint32_t parent_timestamp;
uint32_t reserved;
// Backing file name (in UTF-16)
uint8_t parent_name[512];
struct {
uint32_t platform;
uint32_t data_space;
uint32_t data_length;
uint32_t reserved;
uint64_t data_offset;
} parent_locator[8];
};
typedef struct BDRVVPCState {
CoMutex lock;
uint8_t footer_buf[HEADER_SIZE];
uint64_t free_data_block_offset;
int max_table_entries;
uint32_t *pagetable;
uint64_t bat_offset;
uint64_t last_bitmap_offset;
uint32_t block_size;
uint32_t bitmap_size;
#ifdef CACHE
uint8_t *pageentry_u8;
uint32_t *pageentry_u32;
uint16_t *pageentry_u16;
uint64_t last_bitmap;
#endif
Error *migration_blocker;
} BDRVVPCState;
static uint32_t vpc_checksum(uint8_t* buf, size_t size)
{
uint32_t res = 0;
int i;
for (i = 0; i < size; i++)
res += buf[i];
return ~res;
}
static int vpc_probe(const uint8_t *buf, int buf_size, const char *filename)
{
if (buf_size >= 8 && !strncmp((char *)buf, "conectix", 8))
return 100;
return 0;
}
static int vpc_open(BlockDriverState *bs, int flags)
{
BDRVVPCState *s = bs->opaque;
int i;
struct vhd_footer* footer;
struct vhd_dyndisk_header* dyndisk_header;
uint8_t buf[HEADER_SIZE];
uint32_t checksum;
int err = -1;
int disk_type = VHD_DYNAMIC;
if (bdrv_pread(bs->file, 0, s->footer_buf, HEADER_SIZE) != HEADER_SIZE)
goto fail;
footer = (struct vhd_footer*) s->footer_buf;
if (strncmp(footer->creator, "conectix", 8)) {
int64_t offset = bdrv_getlength(bs->file);
if (offset < HEADER_SIZE) {
goto fail;
}
/* If a fixed disk, the footer is found only at the end of the file */
if (bdrv_pread(bs->file, offset-HEADER_SIZE, s->footer_buf, HEADER_SIZE)
!= HEADER_SIZE) {
goto fail;
}
if (strncmp(footer->creator, "conectix", 8)) {
goto fail;
}
disk_type = VHD_FIXED;
}
checksum = be32_to_cpu(footer->checksum);
footer->checksum = 0;
if (vpc_checksum(s->footer_buf, HEADER_SIZE) != checksum)
fprintf(stderr, "block-vpc: The header checksum of '%s' is "
"incorrect.\n", bs->filename);
/* Write 'checksum' back to footer, or else will leave it with zero. */
footer->checksum = be32_to_cpu(checksum);
// The visible size of a image in Virtual PC depends on the geometry
// rather than on the size stored in the footer (the size in the footer
// is too large usually)
bs->total_sectors = (int64_t)
be16_to_cpu(footer->cyls) * footer->heads * footer->secs_per_cyl;
if (bs->total_sectors >= 65535 * 16 * 255) {
err = -EFBIG;
goto fail;
}
if (disk_type == VHD_DYNAMIC) {
if (bdrv_pread(bs->file, be64_to_cpu(footer->data_offset), buf,
HEADER_SIZE) != HEADER_SIZE) {
goto fail;
}
dyndisk_header = (struct vhd_dyndisk_header *) buf;
if (strncmp(dyndisk_header->magic, "cxsparse", 8)) {
goto fail;
}
s->block_size = be32_to_cpu(dyndisk_header->block_size);
s->bitmap_size = ((s->block_size / (8 * 512)) + 511) & ~511;
s->max_table_entries = be32_to_cpu(dyndisk_header->max_table_entries);
s->pagetable = g_malloc(s->max_table_entries * 4);
s->bat_offset = be64_to_cpu(dyndisk_header->table_offset);
if (bdrv_pread(bs->file, s->bat_offset, s->pagetable,
s->max_table_entries * 4) != s->max_table_entries * 4) {
goto fail;
}
s->free_data_block_offset =
(s->bat_offset + (s->max_table_entries * 4) + 511) & ~511;
for (i = 0; i < s->max_table_entries; i++) {
be32_to_cpus(&s->pagetable[i]);
if (s->pagetable[i] != 0xFFFFFFFF) {
int64_t next = (512 * (int64_t) s->pagetable[i]) +
s->bitmap_size + s->block_size;
if (next > s->free_data_block_offset) {
s->free_data_block_offset = next;
}
}
}
s->last_bitmap_offset = (int64_t) -1;
#ifdef CACHE
s->pageentry_u8 = g_malloc(512);
s->pageentry_u32 = s->pageentry_u8;
s->pageentry_u16 = s->pageentry_u8;
s->last_pagetable = -1;
#endif
}
qemu_co_mutex_init(&s->lock);
/* Disable migration when VHD images are used */
error_set(&s->migration_blocker,
QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
"vpc", bs->device_name, "live migration");
migrate_add_blocker(s->migration_blocker);
return 0;
fail:
return err;
}
/*
* Returns the absolute byte offset of the given sector in the image file.
* If the sector is not allocated, -1 is returned instead.
*
* The parameter write must be 1 if the offset will be used for a write
* operation (the block bitmaps is updated then), 0 otherwise.
*/
static inline int64_t get_sector_offset(BlockDriverState *bs,
int64_t sector_num, int write)
{
BDRVVPCState *s = bs->opaque;
uint64_t offset = sector_num * 512;
uint64_t bitmap_offset, block_offset;
uint32_t pagetable_index, pageentry_index;
pagetable_index = offset / s->block_size;
pageentry_index = (offset % s->block_size) / 512;
if (pagetable_index >= s->max_table_entries || s->pagetable[pagetable_index] == 0xffffffff)
return -1; // not allocated
bitmap_offset = 512 * (uint64_t) s->pagetable[pagetable_index];
block_offset = bitmap_offset + s->bitmap_size + (512 * pageentry_index);
// We must ensure that we don't write to any sectors which are marked as
// unused in the bitmap. We get away with setting all bits in the block
// bitmap each time we write to a new block. This might cause Virtual PC to
// miss sparse read optimization, but it's not a problem in terms of
// correctness.
if (write && (s->last_bitmap_offset != bitmap_offset)) {
uint8_t bitmap[s->bitmap_size];
s->last_bitmap_offset = bitmap_offset;
memset(bitmap, 0xff, s->bitmap_size);
bdrv_pwrite_sync(bs->file, bitmap_offset, bitmap, s->bitmap_size);
}
// printf("sector: %" PRIx64 ", index: %x, offset: %x, bioff: %" PRIx64 ", bloff: %" PRIx64 "\n",
// sector_num, pagetable_index, pageentry_index,
// bitmap_offset, block_offset);
// disabled by reason
#if 0
#ifdef CACHE
if (bitmap_offset != s->last_bitmap)
{
lseek(s->fd, bitmap_offset, SEEK_SET);
s->last_bitmap = bitmap_offset;
// Scary! Bitmap is stored as big endian 32bit entries,
// while we used to look it up byte by byte
read(s->fd, s->pageentry_u8, 512);
for (i = 0; i < 128; i++)
be32_to_cpus(&s->pageentry_u32[i]);
}
if ((s->pageentry_u8[pageentry_index / 8] >> (pageentry_index % 8)) & 1)
return -1;
#else
lseek(s->fd, bitmap_offset + (pageentry_index / 8), SEEK_SET);
read(s->fd, &bitmap_entry, 1);
if ((bitmap_entry >> (pageentry_index % 8)) & 1)
return -1; // not allocated
#endif
#endif
return block_offset;
}
/*
* Writes the footer to the end of the image file. This is needed when the
* file grows as it overwrites the old footer
*
* Returns 0 on success and < 0 on error
*/
static int rewrite_footer(BlockDriverState* bs)
{
int ret;
BDRVVPCState *s = bs->opaque;
int64_t offset = s->free_data_block_offset;
ret = bdrv_pwrite_sync(bs->file, offset, s->footer_buf, HEADER_SIZE);
if (ret < 0)
return ret;
return 0;
}
/*
* Allocates a new block. This involves writing a new footer and updating
* the Block Allocation Table to use the space at the old end of the image
* file (overwriting the old footer)
*
* Returns the sectors' offset in the image file on success and < 0 on error
*/
static int64_t alloc_block(BlockDriverState* bs, int64_t sector_num)
{
BDRVVPCState *s = bs->opaque;
int64_t bat_offset;
uint32_t index, bat_value;
int ret;
uint8_t bitmap[s->bitmap_size];
// Check if sector_num is valid
if ((sector_num < 0) || (sector_num > bs->total_sectors))
return -1;
// Write entry into in-memory BAT
index = (sector_num * 512) / s->block_size;
if (s->pagetable[index] != 0xFFFFFFFF)
return -1;
s->pagetable[index] = s->free_data_block_offset / 512;
// Initialize the block's bitmap
memset(bitmap, 0xff, s->bitmap_size);
ret = bdrv_pwrite_sync(bs->file, s->free_data_block_offset, bitmap,
s->bitmap_size);
if (ret < 0) {
return ret;
}
// Write new footer (the old one will be overwritten)
s->free_data_block_offset += s->block_size + s->bitmap_size;
ret = rewrite_footer(bs);
if (ret < 0)
goto fail;
// Write BAT entry to disk
bat_offset = s->bat_offset + (4 * index);
bat_value = be32_to_cpu(s->pagetable[index]);
ret = bdrv_pwrite_sync(bs->file, bat_offset, &bat_value, 4);
if (ret < 0)
goto fail;
return get_sector_offset(bs, sector_num, 0);
fail:
s->free_data_block_offset -= (s->block_size + s->bitmap_size);
return -1;
}
static int vpc_read(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
BDRVVPCState *s = bs->opaque;
int ret;
int64_t offset;
int64_t sectors, sectors_per_block;
struct vhd_footer *footer = (struct vhd_footer *) s->footer_buf;
if (cpu_to_be32(footer->type) == VHD_FIXED) {
return bdrv_read(bs->file, sector_num, buf, nb_sectors);
}
while (nb_sectors > 0) {
offset = get_sector_offset(bs, sector_num, 0);
sectors_per_block = s->block_size >> BDRV_SECTOR_BITS;
sectors = sectors_per_block - (sector_num % sectors_per_block);
if (sectors > nb_sectors) {
sectors = nb_sectors;
}
if (offset == -1) {
memset(buf, 0, sectors * BDRV_SECTOR_SIZE);
} else {
ret = bdrv_pread(bs->file, offset, buf,
sectors * BDRV_SECTOR_SIZE);
if (ret != sectors * BDRV_SECTOR_SIZE) {
return -1;
}
}
nb_sectors -= sectors;
sector_num += sectors;
buf += sectors * BDRV_SECTOR_SIZE;
}
return 0;
}
static coroutine_fn int vpc_co_read(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
int ret;
BDRVVPCState *s = bs->opaque;
qemu_co_mutex_lock(&s->lock);
ret = vpc_read(bs, sector_num, buf, nb_sectors);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
static int vpc_write(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
BDRVVPCState *s = bs->opaque;
int64_t offset;
int64_t sectors, sectors_per_block;
int ret;
struct vhd_footer *footer = (struct vhd_footer *) s->footer_buf;
if (cpu_to_be32(footer->type) == VHD_FIXED) {
return bdrv_write(bs->file, sector_num, buf, nb_sectors);
}
while (nb_sectors > 0) {
offset = get_sector_offset(bs, sector_num, 1);
sectors_per_block = s->block_size >> BDRV_SECTOR_BITS;
sectors = sectors_per_block - (sector_num % sectors_per_block);
if (sectors > nb_sectors) {
sectors = nb_sectors;
}
if (offset == -1) {
offset = alloc_block(bs, sector_num);
if (offset < 0)
return -1;
}
ret = bdrv_pwrite(bs->file, offset, buf, sectors * BDRV_SECTOR_SIZE);
if (ret != sectors * BDRV_SECTOR_SIZE) {
return -1;
}
nb_sectors -= sectors;
sector_num += sectors;
buf += sectors * BDRV_SECTOR_SIZE;
}
return 0;
}
static coroutine_fn int vpc_co_write(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
int ret;
BDRVVPCState *s = bs->opaque;
qemu_co_mutex_lock(&s->lock);
ret = vpc_write(bs, sector_num, buf, nb_sectors);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
/*
* Calculates the number of cylinders, heads and sectors per cylinder
* based on a given number of sectors. This is the algorithm described
* in the VHD specification.
*
* Note that the geometry doesn't always exactly match total_sectors but
* may round it down.
*
* Returns 0 on success, -EFBIG if the size is larger than 127 GB
*/
static int calculate_geometry(int64_t total_sectors, uint16_t* cyls,
uint8_t* heads, uint8_t* secs_per_cyl)
{
uint32_t cyls_times_heads;
if (total_sectors > 65535 * 16 * 255)
return -EFBIG;
if (total_sectors > 65535 * 16 * 63) {
*secs_per_cyl = 255;
*heads = 16;
cyls_times_heads = total_sectors / *secs_per_cyl;
} else {
*secs_per_cyl = 17;
cyls_times_heads = total_sectors / *secs_per_cyl;
*heads = (cyls_times_heads + 1023) / 1024;
if (*heads < 4)
*heads = 4;
if (cyls_times_heads >= (*heads * 1024) || *heads > 16) {
*secs_per_cyl = 31;
*heads = 16;
cyls_times_heads = total_sectors / *secs_per_cyl;
}
if (cyls_times_heads >= (*heads * 1024)) {
*secs_per_cyl = 63;
*heads = 16;
cyls_times_heads = total_sectors / *secs_per_cyl;
}
}
*cyls = cyls_times_heads / *heads;
return 0;
}
static int create_dynamic_disk(int fd, uint8_t *buf, int64_t total_sectors)
{
struct vhd_dyndisk_header* dyndisk_header =
(struct vhd_dyndisk_header*) buf;
size_t block_size, num_bat_entries;
int i;
int ret = -EIO;
// Write the footer (twice: at the beginning and at the end)
block_size = 0x200000;
num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);
if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) {
goto fail;
}
if (lseek(fd, 1536 + ((num_bat_entries * 4 + 511) & ~511), SEEK_SET) < 0) {
goto fail;
}
if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) {
goto fail;
}
// Write the initial BAT
if (lseek(fd, 3 * 512, SEEK_SET) < 0) {
goto fail;
}
memset(buf, 0xFF, 512);
for (i = 0; i < (num_bat_entries * 4 + 511) / 512; i++) {
if (write(fd, buf, 512) != 512) {
goto fail;
}
}
// Prepare the Dynamic Disk Header
memset(buf, 0, 1024);
memcpy(dyndisk_header->magic, "cxsparse", 8);
/*
* Note: The spec is actually wrong here for data_offset, it says
* 0xFFFFFFFF, but MS tools expect all 64 bits to be set.
*/
dyndisk_header->data_offset = be64_to_cpu(0xFFFFFFFFFFFFFFFFULL);
dyndisk_header->table_offset = be64_to_cpu(3 * 512);
dyndisk_header->version = be32_to_cpu(0x00010000);
dyndisk_header->block_size = be32_to_cpu(block_size);
dyndisk_header->max_table_entries = be32_to_cpu(num_bat_entries);
dyndisk_header->checksum = be32_to_cpu(vpc_checksum(buf, 1024));
// Write the header
if (lseek(fd, 512, SEEK_SET) < 0) {
goto fail;
}
if (write(fd, buf, 1024) != 1024) {
goto fail;
}
ret = 0;
fail:
return ret;
}
static int create_fixed_disk(int fd, uint8_t *buf, int64_t total_size)
{
int ret = -EIO;
/* Add footer to total size */
total_size += 512;
if (ftruncate(fd, total_size) != 0) {
ret = -errno;
goto fail;
}
if (lseek(fd, -512, SEEK_END) < 0) {
goto fail;
}
if (write(fd, buf, HEADER_SIZE) != HEADER_SIZE) {
goto fail;
}
ret = 0;
fail:
return ret;
}
static int vpc_create(const char *filename, QEMUOptionParameter *options)
{
uint8_t buf[1024];
struct vhd_footer *footer = (struct vhd_footer *) buf;
QEMUOptionParameter *disk_type_param;
int fd, i;
uint16_t cyls = 0;
uint8_t heads = 0;
uint8_t secs_per_cyl = 0;
int64_t total_sectors;
int64_t total_size;
int disk_type;
int ret = -EIO;
/* Read out options */
total_size = get_option_parameter(options, BLOCK_OPT_SIZE)->value.n;
disk_type_param = get_option_parameter(options, BLOCK_OPT_SUBFMT);
if (disk_type_param && disk_type_param->value.s) {
if (!strcmp(disk_type_param->value.s, "dynamic")) {
disk_type = VHD_DYNAMIC;
} else if (!strcmp(disk_type_param->value.s, "fixed")) {
disk_type = VHD_FIXED;
} else {
return -EINVAL;
}
} else {
disk_type = VHD_DYNAMIC;
}
/* Create the file */
fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
if (fd < 0) {
return -EIO;
}
/*
* Calculate matching total_size and geometry. Increase the number of
* sectors requested until we get enough (or fail). This ensures that
* qemu-img convert doesn't truncate images, but rather rounds up.
*/
total_sectors = total_size / BDRV_SECTOR_SIZE;
for (i = 0; total_sectors > (int64_t)cyls * heads * secs_per_cyl; i++) {
if (calculate_geometry(total_sectors + i, &cyls, &heads,
&secs_per_cyl))
{
ret = -EFBIG;
goto fail;
}
}
total_sectors = (int64_t) cyls * heads * secs_per_cyl;
/* Prepare the Hard Disk Footer */
memset(buf, 0, 1024);
memcpy(footer->creator, "conectix", 8);
/* TODO Check if "qemu" creator_app is ok for VPC */
memcpy(footer->creator_app, "qemu", 4);
memcpy(footer->creator_os, "Wi2k", 4);
footer->features = be32_to_cpu(0x02);
footer->version = be32_to_cpu(0x00010000);
if (disk_type == VHD_DYNAMIC) {
footer->data_offset = be64_to_cpu(HEADER_SIZE);
} else {
footer->data_offset = be64_to_cpu(0xFFFFFFFFFFFFFFFFULL);
}
footer->timestamp = be32_to_cpu(time(NULL) - VHD_TIMESTAMP_BASE);
/* Version of Virtual PC 2007 */
footer->major = be16_to_cpu(0x0005);
footer->minor = be16_to_cpu(0x0003);
if (disk_type == VHD_DYNAMIC) {
footer->orig_size = be64_to_cpu(total_sectors * 512);
footer->size = be64_to_cpu(total_sectors * 512);
} else {
footer->orig_size = be64_to_cpu(total_size);
footer->size = be64_to_cpu(total_size);
}
footer->cyls = be16_to_cpu(cyls);
footer->heads = heads;
footer->secs_per_cyl = secs_per_cyl;
footer->type = be32_to_cpu(disk_type);
/* TODO uuid is missing */
footer->checksum = be32_to_cpu(vpc_checksum(buf, HEADER_SIZE));
if (disk_type == VHD_DYNAMIC) {
ret = create_dynamic_disk(fd, buf, total_sectors);
} else {
ret = create_fixed_disk(fd, buf, total_size);
}
fail:
close(fd);
return ret;
}
static void vpc_close(BlockDriverState *bs)
{
BDRVVPCState *s = bs->opaque;
g_free(s->pagetable);
#ifdef CACHE
g_free(s->pageentry_u8);
#endif
migrate_del_blocker(s->migration_blocker);
error_free(s->migration_blocker);
}
static QEMUOptionParameter vpc_create_options[] = {
{
.name = BLOCK_OPT_SIZE,
.type = OPT_SIZE,
.help = "Virtual disk size"
},
{
.name = BLOCK_OPT_SUBFMT,
.type = OPT_STRING,
.help =
"Type of virtual hard disk format. Supported formats are "
"{dynamic (default) | fixed} "
},
{ NULL }
};
static BlockDriver bdrv_vpc = {
.format_name = "vpc",
.instance_size = sizeof(BDRVVPCState),
.bdrv_probe = vpc_probe,
.bdrv_open = vpc_open,
.bdrv_close = vpc_close,
.bdrv_create = vpc_create,
.bdrv_read = vpc_co_read,
.bdrv_write = vpc_co_write,
.create_options = vpc_create_options,
};
static void bdrv_vpc_init(void)
{
bdrv_register(&bdrv_vpc);
}
block_init(bdrv_vpc_init);
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