X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=qemu%2Fblock%2Fvpc.c;h=3e2ea698d979846613cc7cf94899136fdc6f9fb0;hb=437fd90c0250dee670290f9b714253671a990160;hp=3e385d9fb991f51847905bd14e22538e80b5df30;hpb=e44e3482bdb4d0ebde2d8b41830ac2cdb07948fb;p=kvmfornfv.git

diff --git a/qemu/block/vpc.c b/qemu/block/vpc.c
index 3e385d9fb..3e2ea698d 100644
--- a/qemu/block/vpc.c
+++ b/qemu/block/vpc.c
@@ -22,8 +22,11 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
+#include "qemu/osdep.h"
+#include "qapi/error.h"
 #include "qemu-common.h"
 #include "block/block_int.h"
+#include "sysemu/block-backend.h"
 #include "qemu/module.h"
 #include "migration/migration.h"
 #if defined(CONFIG_UUID)
@@ -42,28 +45,34 @@ enum vhd_type {
     VHD_DIFFERENCING    = 4,
 };
 
-// Seconds since Jan 1, 2000 0:00:00 (UTC)
+/* Seconds since Jan 1, 2000 0:00:00 (UTC) */
 #define VHD_TIMESTAMP_BASE 946684800
 
-#define VHD_MAX_SECTORS       (65535LL * 255 * 255)
-#define VHD_MAX_GEOMETRY      (65535LL *  16 * 255)
+#define VHD_CHS_MAX_C   65535LL
+#define VHD_CHS_MAX_H   16
+#define VHD_CHS_MAX_S   255
 
-// always big-endian
+#define VHD_MAX_SECTORS       0xff000000    /* 2040 GiB max image size */
+#define VHD_MAX_GEOMETRY      (VHD_CHS_MAX_C * VHD_CHS_MAX_H * VHD_CHS_MAX_S)
+
+#define VPC_OPT_FORCE_SIZE "force_size"
+
+/* always big-endian */
 typedef struct vhd_footer {
-    char        creator[8]; // "conectix"
+    char        creator[8]; /* "conectix" */
     uint32_t    features;
     uint32_t    version;
 
-    // Offset of next header structure, 0xFFFFFFFF if none
+    /* Offset of next header structure, 0xFFFFFFFF if none */
     uint64_t    data_offset;
 
-    // Seconds since Jan 1, 2000 0:00:00 (UTC)
+    /* Seconds since Jan 1, 2000 0:00:00 (UTC) */
     uint32_t    timestamp;
 
-    char        creator_app[4]; // "vpc "
+    char        creator_app[4]; /*  e.g., "vpc " */
     uint16_t    major;
     uint16_t    minor;
-    char        creator_os[4]; // "Wi2k"
+    char        creator_os[4]; /* "Wi2k" */
 
     uint64_t    orig_size;
     uint64_t    current_size;
@@ -74,29 +83,29 @@ typedef struct vhd_footer {
 
     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")
+    /* 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)
+    /* UUID used to identify a parent hard disk (backing file) */
     uint8_t     uuid[16];
 
     uint8_t     in_saved_state;
 } QEMU_PACKED VHDFooter;
 
 typedef struct vhd_dyndisk_header {
-    char        magic[8]; // "cxsparse"
+    char        magic[8]; /* "cxsparse" */
 
-    // Offset of next header structure, 0xFFFFFFFF if none
+    /* Offset of next header structure, 0xFFFFFFFF if none */
     uint64_t    data_offset;
 
-    // Offset of the Block Allocation Table (BAT)
+    /* Offset of the Block Allocation Table (BAT) */
     uint64_t    table_offset;
 
     uint32_t    version;
-    uint32_t    max_table_entries; // 32bit/entry
+    uint32_t    max_table_entries; /* 32bit/entry */
 
-    // 2 MB by default, must be a power of two
+    /* 2 MB by default, must be a power of two */
     uint32_t    block_size;
 
     uint32_t    checksum;
@@ -104,7 +113,7 @@ typedef struct vhd_dyndisk_header {
     uint32_t    parent_timestamp;
     uint32_t    reserved;
 
-    // Backing file name (in UTF-16)
+    /* Backing file name (in UTF-16) */
     uint8_t     parent_name[512];
 
     struct {
@@ -127,6 +136,8 @@ typedef struct BDRVVPCState {
 
     uint32_t block_size;
     uint32_t bitmap_size;
+    bool force_use_chs;
+    bool force_use_sz;
 
 #ifdef CACHE
     uint8_t *pageentry_u8;
@@ -139,6 +150,22 @@ typedef struct BDRVVPCState {
     Error *migration_blocker;
 } BDRVVPCState;
 
+#define VPC_OPT_SIZE_CALC "force_size_calc"
+static QemuOptsList vpc_runtime_opts = {
+    .name = "vpc-runtime-opts",
+    .head = QTAILQ_HEAD_INITIALIZER(vpc_runtime_opts.head),
+    .desc = {
+        {
+            .name = VPC_OPT_SIZE_CALC,
+            .type = QEMU_OPT_STRING,
+            .help = "Force disk size calculation to use either CHS geometry, "
+                    "or use the disk current_size specified in the VHD footer. "
+                    "{chs, current_size}"
+        },
+        { /* end of list */ }
+    }
+};
+
 static uint32_t vpc_checksum(uint8_t* buf, size_t size)
 {
     uint32_t res = 0;
@@ -158,6 +185,25 @@ static int vpc_probe(const uint8_t *buf, int buf_size, const char *filename)
     return 0;
 }
 
+static void vpc_parse_options(BlockDriverState *bs, QemuOpts *opts,
+                              Error **errp)
+{
+    BDRVVPCState *s = bs->opaque;
+    const char *size_calc;
+
+    size_calc = qemu_opt_get(opts, VPC_OPT_SIZE_CALC);
+
+    if (!size_calc) {
+       /* no override, use autodetect only */
+    } else if (!strcmp(size_calc, "current_size")) {
+        s->force_use_sz = true;
+    } else if (!strcmp(size_calc, "chs")) {
+        s->force_use_chs = true;
+    } else {
+        error_setg(errp, "Invalid size calculation mode: '%s'", size_calc);
+    }
+}
+
 static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
@@ -165,6 +211,9 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
     int i;
     VHDFooter *footer;
     VHDDynDiskHeader *dyndisk_header;
+    QemuOpts *opts = NULL;
+    Error *local_err = NULL;
+    bool use_chs;
     uint8_t buf[HEADER_SIZE];
     uint32_t checksum;
     uint64_t computed_size;
@@ -172,24 +221,42 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
     int disk_type = VHD_DYNAMIC;
     int ret;
 
-    ret = bdrv_pread(bs->file, 0, s->footer_buf, HEADER_SIZE);
+    opts = qemu_opts_create(&vpc_runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    vpc_parse_options(bs, opts, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    ret = bdrv_pread(bs->file->bs, 0, s->footer_buf, HEADER_SIZE);
     if (ret < 0) {
+        error_setg(errp, "Unable to read VHD header");
         goto fail;
     }
 
     footer = (VHDFooter *) s->footer_buf;
     if (strncmp(footer->creator, "conectix", 8)) {
-        int64_t offset = bdrv_getlength(bs->file);
+        int64_t offset = bdrv_getlength(bs->file->bs);
         if (offset < 0) {
             ret = offset;
+            error_setg(errp, "Invalid file size");
             goto fail;
         } else if (offset < HEADER_SIZE) {
             ret = -EINVAL;
+            error_setg(errp, "File too small for a VHD header");
             goto fail;
         }
 
         /* If a fixed disk, the footer is found only at the end of the file */
-        ret = bdrv_pread(bs->file, offset-HEADER_SIZE, s->footer_buf,
+        ret = bdrv_pread(bs->file->bs, offset-HEADER_SIZE, s->footer_buf,
                          HEADER_SIZE);
         if (ret < 0) {
             goto fail;
@@ -211,36 +278,66 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
     /* Write 'checksum' back to footer, or else will leave it with zero. */
     footer->checksum = cpu_to_be32(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)
+    /* 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;
 
-    /* Images that have exactly the maximum geometry are probably bigger and
-     * would be truncated if we adhered to the geometry for them. Rely on
-     * footer->current_size for them. */
-    if (bs->total_sectors == VHD_MAX_GEOMETRY) {
+    /* Microsoft Virtual PC and Microsoft Hyper-V produce and read
+     * VHD image sizes differently.  VPC will rely on CHS geometry,
+     * while Hyper-V and disk2vhd use the size specified in the footer.
+     *
+     * We use a couple of approaches to try and determine the correct method:
+     * look at the Creator App field, and look for images that have CHS
+     * geometry that is the maximum value.
+     *
+     * If the CHS geometry is the maximum CHS geometry, then we assume that
+     * the size is the footer->current_size to avoid truncation.  Otherwise,
+     * we follow the table based on footer->creator_app:
+     *
+     *  Known creator apps:
+     *      'vpc '  :  CHS              Virtual PC (uses disk geometry)
+     *      'qemu'  :  CHS              QEMU (uses disk geometry)
+     *      'qem2'  :  current_size     QEMU (uses current_size)
+     *      'win '  :  current_size     Hyper-V
+     *      'd2v '  :  current_size     Disk2vhd
+     *      'tap\0' :  current_size     XenServer
+     *      'CTXS'  :  current_size     XenConverter
+     *
+     *  The user can override the table values via drive options, however
+     *  even with an override we will still use current_size for images
+     *  that have CHS geometry of the maximum size.
+     */
+    use_chs = (!!strncmp(footer->creator_app, "win ", 4) &&
+               !!strncmp(footer->creator_app, "qem2", 4) &&
+               !!strncmp(footer->creator_app, "d2v ", 4) &&
+               !!strncmp(footer->creator_app, "CTXS", 4) &&
+               !!memcmp(footer->creator_app, "tap", 4)) || s->force_use_chs;
+
+    if (!use_chs || bs->total_sectors == VHD_MAX_GEOMETRY || s->force_use_sz) {
         bs->total_sectors = be64_to_cpu(footer->current_size) /
-                            BDRV_SECTOR_SIZE;
+                                        BDRV_SECTOR_SIZE;
     }
 
-    /* Allow a maximum disk size of approximately 2 TB */
-    if (bs->total_sectors >= VHD_MAX_SECTORS) {
+    /* Allow a maximum disk size of 2040 GiB */
+    if (bs->total_sectors > VHD_MAX_SECTORS) {
         ret = -EFBIG;
         goto fail;
     }
 
     if (disk_type == VHD_DYNAMIC) {
-        ret = bdrv_pread(bs->file, be64_to_cpu(footer->data_offset), buf,
+        ret = bdrv_pread(bs->file->bs, be64_to_cpu(footer->data_offset), buf,
                          HEADER_SIZE);
         if (ret < 0) {
+            error_setg(errp, "Error reading dynamic VHD header");
             goto fail;
         }
 
         dyndisk_header = (VHDDynDiskHeader *) buf;
 
         if (strncmp(dyndisk_header->magic, "cxsparse", 8)) {
+            error_setg(errp, "Invalid header magic");
             ret = -EINVAL;
             goto fail;
         }
@@ -256,16 +353,14 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
         s->max_table_entries = be32_to_cpu(dyndisk_header->max_table_entries);
 
         if ((bs->total_sectors * 512) / s->block_size > 0xffffffffU) {
-            ret = -EINVAL;
-            goto fail;
-        }
-        if (s->max_table_entries > (VHD_MAX_SECTORS * 512) / s->block_size) {
+            error_setg(errp, "Too many blocks");
             ret = -EINVAL;
             goto fail;
         }
 
         computed_size = (uint64_t) s->max_table_entries * s->block_size;
         if (computed_size < bs->total_sectors * 512) {
+            error_setg(errp, "Page table too small");
             ret = -EINVAL;
             goto fail;
         }
@@ -280,16 +375,19 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
 
         pagetable_size = (uint64_t) s->max_table_entries * 4;
 
-        s->pagetable = qemu_try_blockalign(bs->file, pagetable_size);
+        s->pagetable = qemu_try_blockalign(bs->file->bs, pagetable_size);
         if (s->pagetable == NULL) {
+            error_setg(errp, "Unable to allocate memory for page table");
             ret = -ENOMEM;
             goto fail;
         }
 
         s->bat_offset = be64_to_cpu(dyndisk_header->table_offset);
 
-        ret = bdrv_pread(bs->file, s->bat_offset, s->pagetable, pagetable_size);
+        ret = bdrv_pread(bs->file->bs, s->bat_offset, s->pagetable,
+                         pagetable_size);
         if (ret < 0) {
+            error_setg(errp, "Error reading pagetable");
             goto fail;
         }
 
@@ -308,7 +406,7 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
             }
         }
 
-        if (s->free_data_block_offset > bdrv_getlength(bs->file)) {
+        if (s->free_data_block_offset > bdrv_getlength(bs->file->bs)) {
             error_setg(errp, "block-vpc: free_data_block_offset points after "
                              "the end of file. The image has been truncated.");
             ret = -EINVAL;
@@ -368,22 +466,22 @@ static inline int64_t get_sector_offset(BlockDriverState *bs,
     pageentry_index = (offset % s->block_size) / 512;
 
     if (pagetable_index >= s->max_table_entries || s->pagetable[pagetable_index] == 0xffffffff)
-        return -1; // not allocated
+        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.
+    /* 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);
+        bdrv_pwrite_sync(bs->file->bs, bitmap_offset, bitmap, s->bitmap_size);
     }
 
     return block_offset;
@@ -401,7 +499,7 @@ static int rewrite_footer(BlockDriverState* bs)
     BDRVVPCState *s = bs->opaque;
     int64_t offset = s->free_data_block_offset;
 
-    ret = bdrv_pwrite_sync(bs->file, offset, s->footer_buf, HEADER_SIZE);
+    ret = bdrv_pwrite_sync(bs->file->bs, offset, s->footer_buf, HEADER_SIZE);
     if (ret < 0)
         return ret;
 
@@ -423,35 +521,35 @@ static int64_t alloc_block(BlockDriverState* bs, int64_t sector_num)
     int ret;
     uint8_t bitmap[s->bitmap_size];
 
-    // Check if sector_num is valid
+    /* Check if sector_num is valid */
     if ((sector_num < 0) || (sector_num > bs->total_sectors))
         return -1;
 
-    // Write entry into in-memory BAT
+    /* 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
+    /* Initialize the block's bitmap */
     memset(bitmap, 0xff, s->bitmap_size);
-    ret = bdrv_pwrite_sync(bs->file, s->free_data_block_offset, bitmap,
+    ret = bdrv_pwrite_sync(bs->file->bs, s->free_data_block_offset, bitmap,
         s->bitmap_size);
     if (ret < 0) {
         return ret;
     }
 
-    // Write new footer (the old one will be overwritten)
+    /* 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
+    /* Write BAT entry to disk */
     bat_offset = s->bat_offset + (4 * index);
     bat_value = cpu_to_be32(s->pagetable[index]);
-    ret = bdrv_pwrite_sync(bs->file, bat_offset, &bat_value, 4);
+    ret = bdrv_pwrite_sync(bs->file->bs, bat_offset, &bat_value, 4);
     if (ret < 0)
         goto fail;
 
@@ -485,7 +583,7 @@ static int vpc_read(BlockDriverState *bs, int64_t sector_num,
     VHDFooter *footer = (VHDFooter *) s->footer_buf;
 
     if (be32_to_cpu(footer->type) == VHD_FIXED) {
-        return bdrv_read(bs->file, sector_num, buf, nb_sectors);
+        return bdrv_read(bs->file->bs, sector_num, buf, nb_sectors);
     }
     while (nb_sectors > 0) {
         offset = get_sector_offset(bs, sector_num, 0);
@@ -499,7 +597,7 @@ static int vpc_read(BlockDriverState *bs, int64_t sector_num,
         if (offset == -1) {
             memset(buf, 0, sectors * BDRV_SECTOR_SIZE);
         } else {
-            ret = bdrv_pread(bs->file, offset, buf,
+            ret = bdrv_pread(bs->file->bs, offset, buf,
                 sectors * BDRV_SECTOR_SIZE);
             if (ret != sectors * BDRV_SECTOR_SIZE) {
                 return -1;
@@ -534,7 +632,7 @@ static int vpc_write(BlockDriverState *bs, int64_t sector_num,
     VHDFooter *footer =  (VHDFooter *) s->footer_buf;
 
     if (be32_to_cpu(footer->type) == VHD_FIXED) {
-        return bdrv_write(bs->file, sector_num, buf, nb_sectors);
+        return bdrv_write(bs->file->bs, sector_num, buf, nb_sectors);
     }
     while (nb_sectors > 0) {
         offset = get_sector_offset(bs, sector_num, 1);
@@ -551,7 +649,8 @@ static int vpc_write(BlockDriverState *bs, int64_t sector_num,
                 return -1;
         }
 
-        ret = bdrv_pwrite(bs->file, offset, buf, sectors * BDRV_SECTOR_SIZE);
+        ret = bdrv_pwrite(bs->file->bs, offset, buf,
+                          sectors * BDRV_SECTOR_SIZE);
         if (ret != sectors * BDRV_SECTOR_SIZE) {
             return -1;
         }
@@ -576,7 +675,7 @@ static coroutine_fn int vpc_co_write(BlockDriverState *bs, int64_t sector_num,
 }
 
 static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *pnum)
+        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
 {
     BDRVVPCState *s = bs->opaque;
     VHDFooter *footer = (VHDFooter*) s->footer_buf;
@@ -586,6 +685,7 @@ static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs,
 
     if (be32_to_cpu(footer->type) == VHD_FIXED) {
         *pnum = nb_sectors;
+        *file = bs->file->bs;
         return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA |
                (sector_num << BDRV_SECTOR_BITS);
     }
@@ -607,6 +707,7 @@ static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs,
         /* *pnum can't be greater than one block for allocated
          * sectors since there is always a bitmap in between. */
         if (allocated) {
+            *file = bs->file->bs;
             return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start;
         }
         if (nb_sectors == 0) {
@@ -626,7 +727,7 @@ static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs,
  * 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 ~2 TB. Override
+ * Returns 0 on success, -EFBIG if the size is larger than 2040 GiB. Override
  * the hardware EIDE and ATA-2 limit of 16 heads (max disk size of 127 GB)
  * and instead allow up to 255 heads.
  */
@@ -668,7 +769,7 @@ static int calculate_geometry(int64_t total_sectors, uint16_t* cyls,
     return 0;
 }
 
-static int create_dynamic_disk(BlockDriverState *bs, uint8_t *buf,
+static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf,
                                int64_t total_sectors)
 {
     VHDDynDiskHeader *dyndisk_header =
@@ -678,34 +779,34 @@ static int create_dynamic_disk(BlockDriverState *bs, uint8_t *buf,
     int ret;
     int64_t offset = 0;
 
-    // Write the footer (twice: at the beginning and at the end)
+    /* 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);
 
-    ret = bdrv_pwrite_sync(bs, offset, buf, HEADER_SIZE);
-    if (ret) {
+    ret = blk_pwrite(blk, offset, buf, HEADER_SIZE);
+    if (ret < 0) {
         goto fail;
     }
 
     offset = 1536 + ((num_bat_entries * 4 + 511) & ~511);
-    ret = bdrv_pwrite_sync(bs, offset, buf, HEADER_SIZE);
+    ret = blk_pwrite(blk, offset, buf, HEADER_SIZE);
     if (ret < 0) {
         goto fail;
     }
 
-    // Write the initial BAT
+    /* Write the initial BAT */
     offset = 3 * 512;
 
     memset(buf, 0xFF, 512);
     for (i = 0; i < (num_bat_entries * 4 + 511) / 512; i++) {
-        ret = bdrv_pwrite_sync(bs, offset, buf, 512);
+        ret = blk_pwrite(blk, offset, buf, 512);
         if (ret < 0) {
             goto fail;
         }
         offset += 512;
     }
 
-    // Prepare the Dynamic Disk Header
+    /* Prepare the Dynamic Disk Header */
     memset(buf, 0, 1024);
 
     memcpy(dyndisk_header->magic, "cxsparse", 8);
@@ -722,10 +823,10 @@ static int create_dynamic_disk(BlockDriverState *bs, uint8_t *buf,
 
     dyndisk_header->checksum = cpu_to_be32(vpc_checksum(buf, 1024));
 
-    // Write the header
+    /* Write the header */
     offset = 512;
 
-    ret = bdrv_pwrite_sync(bs, offset, buf, 1024);
+    ret = blk_pwrite(blk, offset, buf, 1024);
     if (ret < 0) {
         goto fail;
     }
@@ -734,7 +835,7 @@ static int create_dynamic_disk(BlockDriverState *bs, uint8_t *buf,
     return ret;
 }
 
-static int create_fixed_disk(BlockDriverState *bs, uint8_t *buf,
+static int create_fixed_disk(BlockBackend *blk, uint8_t *buf,
                              int64_t total_size)
 {
     int ret;
@@ -742,12 +843,12 @@ static int create_fixed_disk(BlockDriverState *bs, uint8_t *buf,
     /* Add footer to total size */
     total_size += HEADER_SIZE;
 
-    ret = bdrv_truncate(bs, total_size);
+    ret = blk_truncate(blk, total_size);
     if (ret < 0) {
         return ret;
     }
 
-    ret = bdrv_pwrite_sync(bs, total_size - HEADER_SIZE, buf, HEADER_SIZE);
+    ret = blk_pwrite(blk, total_size - HEADER_SIZE, buf, HEADER_SIZE);
     if (ret < 0) {
         return ret;
     }
@@ -768,8 +869,9 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     int64_t total_size;
     int disk_type;
     int ret = -EIO;
+    bool force_size;
     Error *local_err = NULL;
-    BlockDriverState *bs = NULL;
+    BlockBackend *blk = NULL;
 
     /* Read out options */
     total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
@@ -781,6 +883,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
         } else if (!strcmp(disk_type_param, "fixed")) {
             disk_type = VHD_FIXED;
         } else {
+            error_setg(errp, "Invalid disk type, %s", disk_type_param);
             ret = -EINVAL;
             goto out;
         }
@@ -788,36 +891,50 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
         disk_type = VHD_DYNAMIC;
     }
 
+    force_size = qemu_opt_get_bool_del(opts, VPC_OPT_FORCE_SIZE, false);
+
     ret = bdrv_create_file(filename, opts, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto out;
     }
-    ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
-                    NULL, &local_err);
-    if (ret < 0) {
+
+    blk = blk_new_open(filename, NULL, NULL,
+                       BDRV_O_RDWR | BDRV_O_PROTOCOL, &local_err);
+    if (blk == NULL) {
         error_propagate(errp, local_err);
+        ret = -EIO;
         goto out;
     }
 
+    blk_set_allow_write_beyond_eof(blk, true);
+
     /*
      * 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.
      *
-     * If the image size can't be represented by a spec conform CHS geometry,
+     * If the image size can't be represented by a spec conformant CHS geometry,
      * we set the geometry to 65535 x 16 x 255 (CxHxS) sectors and use
      * the image size from the VHD footer to calculate total_sectors.
      */
-    total_sectors = MIN(VHD_MAX_GEOMETRY, total_size / BDRV_SECTOR_SIZE);
-    for (i = 0; total_sectors > (int64_t)cyls * heads * secs_per_cyl; i++) {
-        calculate_geometry(total_sectors + i, &cyls, &heads, &secs_per_cyl);
+    if (force_size) {
+        /* This will force the use of total_size for sector count, below */
+        cyls         = VHD_CHS_MAX_C;
+        heads        = VHD_CHS_MAX_H;
+        secs_per_cyl = VHD_CHS_MAX_S;
+    } else {
+        total_sectors = MIN(VHD_MAX_GEOMETRY, total_size / BDRV_SECTOR_SIZE);
+        for (i = 0; total_sectors > (int64_t)cyls * heads * secs_per_cyl; i++) {
+            calculate_geometry(total_sectors + i, &cyls, &heads, &secs_per_cyl);
+        }
     }
 
     if ((int64_t)cyls * heads * secs_per_cyl == VHD_MAX_GEOMETRY) {
         total_sectors = total_size / BDRV_SECTOR_SIZE;
-        /* Allow a maximum disk size of approximately 2 TB */
+        /* Allow a maximum disk size of 2040 GiB */
         if (total_sectors > VHD_MAX_SECTORS) {
+            error_setg(errp, "Disk size is too large, max size is 2040 GiB");
             ret = -EFBIG;
             goto out;
         }
@@ -830,8 +947,11 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     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);
+    if (force_size) {
+        memcpy(footer->creator_app, "qem2", 4);
+    } else {
+        memcpy(footer->creator_app, "qemu", 4);
+    }
     memcpy(footer->creator_os, "Wi2k", 4);
 
     footer->features = cpu_to_be32(0x02);
@@ -861,13 +981,16 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     footer->checksum = cpu_to_be32(vpc_checksum(buf, HEADER_SIZE));
 
     if (disk_type == VHD_DYNAMIC) {
-        ret = create_dynamic_disk(bs, buf, total_sectors);
+        ret = create_dynamic_disk(blk, buf, total_sectors);
     } else {
-        ret = create_fixed_disk(bs, buf, total_size);
+        ret = create_fixed_disk(blk, buf, total_size);
+    }
+    if (ret < 0) {
+        error_setg(errp, "Unable to create or write VHD header");
     }
 
 out:
-    bdrv_unref(bs);
+    blk_unref(blk);
     g_free(disk_type_param);
     return ret;
 }
@@ -878,7 +1001,7 @@ static int vpc_has_zero_init(BlockDriverState *bs)
     VHDFooter *footer =  (VHDFooter *) s->footer_buf;
 
     if (be32_to_cpu(footer->type) == VHD_FIXED) {
-        return bdrv_has_zero_init(bs->file);
+        return bdrv_has_zero_init(bs->file->bs);
     } else {
         return 1;
     }
@@ -912,6 +1035,13 @@ static QemuOptsList vpc_create_opts = {
                 "Type of virtual hard disk format. Supported formats are "
                 "{dynamic (default) | fixed} "
         },
+        {
+            .name = VPC_OPT_FORCE_SIZE,
+            .type = QEMU_OPT_BOOL,
+            .help = "Force disk size calculation to use the actual size "
+                    "specified, rather than using the nearest CHS-based "
+                    "calculation"
+        },
         { /* end of list */ }
     }
 };