[Qemu-devel] [PULL 0/4] Block patches for 1.2-rc1

[Qemu-devel] [PULL 0/4] Block patches for 1.2-rc1

[Kevin Wolf]

The following changes since commit 731dc9ecd4f2c3041538f7eb2d10eee0cb82da1b:

  Update version to 1.2.0-rc0 (2012-08-16 13:56:34 -0500)

are available in the git repository at:
  http://repo.or.cz/r/qemu/kevin.git for-anthony

Kevin Wolf (3):
      vmdk: Fix header structure
      vmdk: Read footer for streamOptimized images
      Documentation: Warn against qemu-img on active image

Stefan Hajnoczi (1):
      virtio-blk: hide VIRTIO_BLK_F_CONFIG_WCE from old machine types

 block/vmdk.c    |   58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 hw/pc_piix.c    |    4 +++
 hw/virtio-blk.c |    4 ++-
 hw/virtio-blk.h |    1 +
 hw/virtio-pci.c |    1 +
 qemu-img.texi   |    8 +++++++
 6 files changed, 74 insertions(+), 2 deletions(-)

[Qemu-devel] [PATCH 1/4] vmdk: Fix header structure

[Kevin Wolf]

Commit bb45ded9 swapped gd_offset and rgd_offset. This is wrong.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/vmdk.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index daee426..9648398 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -57,8 +57,8 @@ typedef struct {
     int64_t desc_offset;
     int64_t desc_size;
     int32_t num_gtes_per_gte;
-    int64_t gd_offset;
     int64_t rgd_offset;
+    int64_t gd_offset;
     int64_t grain_offset;
     char filler[1];
     char check_bytes[4];
-- 
1.7.6.5

[Qemu-devel] [PATCH 2/4] vmdk: Read footer for streamOptimized images

[Kevin Wolf]

The footer takes precedence over the header when it exists. It contains
the real grain directory offset that is missing in the header. Without
this patch, streamOptimized images with a footer cannot be read.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
---
 block/vmdk.c |   56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index 9648398..bba4c61 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -35,6 +35,7 @@
 #define VMDK4_FLAG_RGD (1 << 1)
 #define VMDK4_FLAG_COMPRESS (1 << 16)
 #define VMDK4_FLAG_MARKER (1 << 17)
+#define VMDK4_GD_AT_END 0xffffffffffffffffULL
 
 typedef struct {
     uint32_t version;
@@ -115,6 +116,13 @@ typedef struct VmdkGrainMarker {
     uint8_t  data[0];
 } VmdkGrainMarker;
 
+enum {
+    MARKER_END_OF_STREAM    = 0,
+    MARKER_GRAIN_TABLE      = 1,
+    MARKER_GRAIN_DIRECTORY  = 2,
+    MARKER_FOOTER           = 3,
+};
+
 static int vmdk_probe(const uint8_t *buf, int buf_size, const char *filename)
 {
     uint32_t magic;
@@ -451,6 +459,54 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
     if (header.capacity == 0 && header.desc_offset) {
         return vmdk_open_desc_file(bs, flags, header.desc_offset << 9);
     }
+
+    if (le64_to_cpu(header.gd_offset) == VMDK4_GD_AT_END) {
+        /*
+         * The footer takes precedence over the header, so read it in. The
+         * footer starts at offset -1024 from the end: One sector for the
+         * footer, and another one for the end-of-stream marker.
+         */
+        struct {
+            struct {
+                uint64_t val;
+                uint32_t size;
+                uint32_t type;
+                uint8_t pad[512 - 16];
+            } QEMU_PACKED footer_marker;
+
+            uint32_t magic;
+            VMDK4Header header;
+            uint8_t pad[512 - 4 - sizeof(VMDK4Header)];
+
+            struct {
+                uint64_t val;
+                uint32_t size;
+                uint32_t type;
+                uint8_t pad[512 - 16];
+            } QEMU_PACKED eos_marker;
+        } QEMU_PACKED footer;
+
+        ret = bdrv_pread(file,
+            bs->file->total_sectors * 512 - 1536,
+            &footer, sizeof(footer));
+        if (ret < 0) {
+            return ret;
+        }
+
+        /* Some sanity checks for the footer */
+        if (be32_to_cpu(footer.magic) != VMDK4_MAGIC ||
+            le32_to_cpu(footer.footer_marker.size) != 0  ||
+            le32_to_cpu(footer.footer_marker.type) != MARKER_FOOTER ||
+            le64_to_cpu(footer.eos_marker.val) != 0  ||
+            le32_to_cpu(footer.eos_marker.size) != 0  ||
+            le32_to_cpu(footer.eos_marker.type) != MARKER_END_OF_STREAM)
+        {
+            return -EINVAL;
+        }
+
+        header = footer.header;
+    }
+
     l1_entry_sectors = le32_to_cpu(header.num_gtes_per_gte)
                         * le64_to_cpu(header.granularity);
     if (l1_entry_sectors == 0) {
-- 
1.7.6.5

[Qemu-devel] [PATCH 3/4] Documentation: Warn against qemu-img on active image

[Kevin Wolf]

People have repeatedly expected that you can do things like snapshotting
an image with qemu-img while a qemu instance is running. Maybe we need
to consider locking the files while they are in use, but having a
warning in the qemu-img manpage is doable for 1.2 and can't hurt anyway.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 qemu-img.texi |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/qemu-img.texi b/qemu-img.texi
index 77c6d0b..77b2c47 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -4,6 +4,14 @@ usage: qemu-img command [command options]
 @c man end
 @end example
 
+@c man begin DESCRIPTION
+qemu-img allows you to create, convert and modify images offline. It can handle
+all image formats supported by QEMU.
+
+@b{Warning:} Never use qemu-img to modify images in use by a running virtual
+machine or any other process; this may destroy the image.
+@c man end
+
 @c man begin OPTIONS
 
 The following commands are supported:
-- 
1.7.6.5

[Qemu-devel] [PATCH 4/4] virtio-blk: hide VIRTIO_BLK_F_CONFIG_WCE from old machine types

[Kevin Wolf]

From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

QEMU has a policy of keeping a stable guest device ABI.  When new guest device
features are introduced they must not change hardware info seen by existing
guests.  This is important because operating systems or applications may
"fingerprint" the hardware and refuse to run when the hardware changes.  To
always get the latest guest device ABI, run with x86 machine type "pc".

This patch hides the new VIRTIO_BLK_F_CONFIG_WCE virtio feature bit from
existing machine types.  Only pc-1.2 and later will expose this feature
by default.

For more info on the VIRTIO_BLK_F_CONFIG_WCE feature bit, see:

  commit 13e3dce068773c971ff2f19d986378c55897c4a3
  Author: Paolo Bonzini <pbonzini@redhat.com>
  Date:   Thu Aug 9 16:07:19 2012 +0200

      virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE

      Also rename VIRTIO_BLK_F_WCACHE to VIRTIO_BLK_F_WCE for consistency with
      the spec.

      Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
      Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Anthony Liguori <aliguori@us.ibm.com> reported:

  This broke qemu-test because it changed the pc-1.0 machine type:

  Setting guest RANDOM seed to 47167
  *** Running tests ***
  Running test /tests/finger-print.sh...		OK
  --- fingerprints/pc-1.0.x86_64	2011-12-18 13:08:40.000000000 -0600
  +++ fingerprint.txt	2012-08-12 13:30:48.000000000 -0500
  @@ -55,7 +55,7 @@
   /sys/bus/pci/devices/0000:00:06.0/subsystem_device=0x0002
   /sys/bus/pci/devices/0000:00:06.0/class=0x010000
   /sys/bus/pci/devices/0000:00:06.0/revision=0x00
  -/sys/bus/pci/devices/0000:00:06.0/virtio/host-features=0x710006d4
  +/sys/bus/pci/devices/0000:00:06.0/virtio/host-features=0x71000ed4
   /sys/class/dmi/id/bios_vendor=Bochs
   /sys/class/dmi/id/bios_date=01/01/2007
   /sys/class/dmi/id/bios_version=Bochs
  Guest fingerprint changed for pc-1.0!

Reported-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 hw/pc_piix.c    |    4 ++++
 hw/virtio-blk.c |    4 +++-
 hw/virtio-blk.h |    1 +
 hw/virtio-pci.c |    1 +
 4 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/hw/pc_piix.c b/hw/pc_piix.c
index 0c0096f..d68dbb2 100644
--- a/hw/pc_piix.c
+++ b/hw/pc_piix.c
@@ -375,6 +375,10 @@ static QEMUMachine pc_machine_v1_2 = {
             .driver   = "qxl",\
             .property = "vgamem_mb",\
             .value    = stringify(8),\
+        },{\
+            .driver   = "virtio-blk-pci",\
+            .property = "config-wce",\
+            .value    = "off",\
         }
 
 static QEMUMachine pc_machine_v1_1 = {
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index fd8fa90..0bc2b5e 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -533,7 +533,9 @@ static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
     features |= (1 << VIRTIO_BLK_F_BLK_SIZE);
     features |= (1 << VIRTIO_BLK_F_SCSI);
 
-    features |= (1 << VIRTIO_BLK_F_CONFIG_WCE);
+    if (s->blk->config_wce) {
+        features |= (1 << VIRTIO_BLK_F_CONFIG_WCE);
+    }
     if (bdrv_enable_write_cache(s->bs))
         features |= (1 << VIRTIO_BLK_F_WCE);
 
diff --git a/hw/virtio-blk.h b/hw/virtio-blk.h
index 35834cf..454f445 100644
--- a/hw/virtio-blk.h
+++ b/hw/virtio-blk.h
@@ -104,6 +104,7 @@ struct VirtIOBlkConf
     BlockConf conf;
     char *serial;
     uint32_t scsi;
+    uint32_t config_wce;
 };
 
 #define DEFINE_VIRTIO_BLK_FEATURES(_state, _field) \
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 5e6e09e..2a3d86f 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -886,6 +886,7 @@ static Property virtio_blk_properties[] = {
 #ifdef __linux__
     DEFINE_PROP_BIT("scsi", VirtIOPCIProxy, blk.scsi, 0, true),
 #endif
+    DEFINE_PROP_BIT("config-wce", VirtIOPCIProxy, blk.config_wce, 0, true),
     DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
     DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
     DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features),
-- 
1.7.6.5

Re: [Qemu-devel] [PATCH 4/4] virtio-blk: hide VIRTIO_BLK_F_CONFIG_WCE from old machine types

[Paolo Bonzini]

Il 17/08/2012 21:25, Kevin Wolf ha scritto:
> From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> 
> QEMU has a policy of keeping a stable guest device ABI.  When new guest device
> features are introduced they must not change hardware info seen by existing
> guests.  This is important because operating systems or applications may
> "fingerprint" the hardware and refuse to run when the hardware changes.  To
> always get the latest guest device ABI, run with x86 machine type "pc".
> 
> This patch hides the new VIRTIO_BLK_F_CONFIG_WCE virtio feature bit from
> existing machine types.  Only pc-1.2 and later will expose this feature
> by default.
> 
> For more info on the VIRTIO_BLK_F_CONFIG_WCE feature bit, see:
> 
>   commit 13e3dce068773c971ff2f19d986378c55897c4a3
>   Author: Paolo Bonzini <pbonzini@redhat.com>
>   Date:   Thu Aug 9 16:07:19 2012 +0200
> 
>       virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE
> 
>       Also rename VIRTIO_BLK_F_WCACHE to VIRTIO_BLK_F_WCE for consistency with
>       the spec.
> 
>       Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>       Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> 
> Anthony Liguori <aliguori@us.ibm.com> reported:
> 
>   This broke qemu-test because it changed the pc-1.0 machine type:
> 
>   Setting guest RANDOM seed to 47167
>   *** Running tests ***
>   Running test /tests/finger-print.sh...		OK
>   --- fingerprints/pc-1.0.x86_64	2011-12-18 13:08:40.000000000 -0600
>   +++ fingerprint.txt	2012-08-12 13:30:48.000000000 -0500
>   @@ -55,7 +55,7 @@
>    /sys/bus/pci/devices/0000:00:06.0/subsystem_device=0x0002
>    /sys/bus/pci/devices/0000:00:06.0/class=0x010000
>    /sys/bus/pci/devices/0000:00:06.0/revision=0x00
>   -/sys/bus/pci/devices/0000:00:06.0/virtio/host-features=0x710006d4
>   +/sys/bus/pci/devices/0000:00:06.0/virtio/host-features=0x71000ed4
>    /sys/class/dmi/id/bios_vendor=Bochs
>    /sys/class/dmi/id/bios_date=01/01/2007
>    /sys/class/dmi/id/bios_version=Bochs
>   Guest fingerprint changed for pc-1.0!
> 
> Reported-by: Anthony Liguori <aliguori@us.ibm.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  hw/pc_piix.c    |    4 ++++
>  hw/virtio-blk.c |    4 +++-
>  hw/virtio-blk.h |    1 +
>  hw/virtio-pci.c |    1 +
>  4 files changed, 9 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> index 0c0096f..d68dbb2 100644
> --- a/hw/pc_piix.c
> +++ b/hw/pc_piix.c
> @@ -375,6 +375,10 @@ static QEMUMachine pc_machine_v1_2 = {
>              .driver   = "qxl",\
>              .property = "vgamem_mb",\
>              .value    = stringify(8),\
> +        },{\
> +            .driver   = "virtio-blk-pci",\
> +            .property = "config-wce",\
> +            .value    = "off",\
>          }
>  
>  static QEMUMachine pc_machine_v1_1 = {
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index fd8fa90..0bc2b5e 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -533,7 +533,9 @@ static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
>      features |= (1 << VIRTIO_BLK_F_BLK_SIZE);
>      features |= (1 << VIRTIO_BLK_F_SCSI);
>  
> -    features |= (1 << VIRTIO_BLK_F_CONFIG_WCE);
> +    if (s->blk->config_wce) {
> +        features |= (1 << VIRTIO_BLK_F_CONFIG_WCE);
> +    }
>      if (bdrv_enable_write_cache(s->bs))
>          features |= (1 << VIRTIO_BLK_F_WCE);
>  
> diff --git a/hw/virtio-blk.h b/hw/virtio-blk.h
> index 35834cf..454f445 100644
> --- a/hw/virtio-blk.h
> +++ b/hw/virtio-blk.h
> @@ -104,6 +104,7 @@ struct VirtIOBlkConf
>      BlockConf conf;
>      char *serial;
>      uint32_t scsi;
> +    uint32_t config_wce;
>  };
>  
>  #define DEFINE_VIRTIO_BLK_FEATURES(_state, _field) \
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 5e6e09e..2a3d86f 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -886,6 +886,7 @@ static Property virtio_blk_properties[] = {
>  #ifdef __linux__
>      DEFINE_PROP_BIT("scsi", VirtIOPCIProxy, blk.scsi, 0, true),
>  #endif
> +    DEFINE_PROP_BIT("config-wce", VirtIOPCIProxy, blk.config_wce, 0, true),
>      DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
>      DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
>      DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features),
> 

Could/should this be added to DEFINE_VIRTIO_BLK_FEATURES instead?  You
don't need the new field, and virtio_blk_get_features can simply omit
VIRTIO_BLK_F_CONFIG_WCE.  At least that's how virtio-net does it.

It can be done in 1.3 though.

Paolo

Re: [Qemu-devel] [PATCH 4/4] virtio-blk: hide VIRTIO_BLK_F_CONFIG_WCE from old machine types

[Stefan Hajnoczi]

On Mon, Aug 20, 2012 at 1:46 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Il 17/08/2012 21:25, Kevin Wolf ha scritto:
>> From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
>>
>> QEMU has a policy of keeping a stable guest device ABI.  When new guest device
>> features are introduced they must not change hardware info seen by existing
>> guests.  This is important because operating systems or applications may
>> "fingerprint" the hardware and refuse to run when the hardware changes.  To
>> always get the latest guest device ABI, run with x86 machine type "pc".
>>
>> This patch hides the new VIRTIO_BLK_F_CONFIG_WCE virtio feature bit from
>> existing machine types.  Only pc-1.2 and later will expose this feature
>> by default.
>>
>> For more info on the VIRTIO_BLK_F_CONFIG_WCE feature bit, see:
>>
>>   commit 13e3dce068773c971ff2f19d986378c55897c4a3
>>   Author: Paolo Bonzini <pbonzini@redhat.com>
>>   Date:   Thu Aug 9 16:07:19 2012 +0200
>>
>>       virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE
>>
>>       Also rename VIRTIO_BLK_F_WCACHE to VIRTIO_BLK_F_WCE for consistency with
>>       the spec.
>>
>>       Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>       Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>
>> Anthony Liguori <aliguori@us.ibm.com> reported:
>>
>>   This broke qemu-test because it changed the pc-1.0 machine type:
>>
>>   Setting guest RANDOM seed to 47167
>>   *** Running tests ***
>>   Running test /tests/finger-print.sh...              OK
>>   --- fingerprints/pc-1.0.x86_64      2011-12-18 13:08:40.000000000 -0600
>>   +++ fingerprint.txt 2012-08-12 13:30:48.000000000 -0500
>>   @@ -55,7 +55,7 @@
>>    /sys/bus/pci/devices/0000:00:06.0/subsystem_device=0x0002
>>    /sys/bus/pci/devices/0000:00:06.0/class=0x010000
>>    /sys/bus/pci/devices/0000:00:06.0/revision=0x00
>>   -/sys/bus/pci/devices/0000:00:06.0/virtio/host-features=0x710006d4
>>   +/sys/bus/pci/devices/0000:00:06.0/virtio/host-features=0x71000ed4
>>    /sys/class/dmi/id/bios_vendor=Bochs
>>    /sys/class/dmi/id/bios_date=01/01/2007
>>    /sys/class/dmi/id/bios_version=Bochs
>>   Guest fingerprint changed for pc-1.0!
>>
>> Reported-by: Anthony Liguori <aliguori@us.ibm.com>
>> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>> ---
>>  hw/pc_piix.c    |    4 ++++
>>  hw/virtio-blk.c |    4 +++-
>>  hw/virtio-blk.h |    1 +
>>  hw/virtio-pci.c |    1 +
>>  4 files changed, 9 insertions(+), 1 deletions(-)
>>
>> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
>> index 0c0096f..d68dbb2 100644
>> --- a/hw/pc_piix.c
>> +++ b/hw/pc_piix.c
>> @@ -375,6 +375,10 @@ static QEMUMachine pc_machine_v1_2 = {
>>              .driver   = "qxl",\
>>              .property = "vgamem_mb",\
>>              .value    = stringify(8),\
>> +        },{\
>> +            .driver   = "virtio-blk-pci",\
>> +            .property = "config-wce",\
>> +            .value    = "off",\
>>          }
>>
>>  static QEMUMachine pc_machine_v1_1 = {
>> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
>> index fd8fa90..0bc2b5e 100644
>> --- a/hw/virtio-blk.c
>> +++ b/hw/virtio-blk.c
>> @@ -533,7 +533,9 @@ static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
>>      features |= (1 << VIRTIO_BLK_F_BLK_SIZE);
>>      features |= (1 << VIRTIO_BLK_F_SCSI);
>>
>> -    features |= (1 << VIRTIO_BLK_F_CONFIG_WCE);
>> +    if (s->blk->config_wce) {
>> +        features |= (1 << VIRTIO_BLK_F_CONFIG_WCE);
>> +    }
>>      if (bdrv_enable_write_cache(s->bs))
>>          features |= (1 << VIRTIO_BLK_F_WCE);
>>
>> diff --git a/hw/virtio-blk.h b/hw/virtio-blk.h
>> index 35834cf..454f445 100644
>> --- a/hw/virtio-blk.h
>> +++ b/hw/virtio-blk.h
>> @@ -104,6 +104,7 @@ struct VirtIOBlkConf
>>      BlockConf conf;
>>      char *serial;
>>      uint32_t scsi;
>> +    uint32_t config_wce;
>>  };
>>
>>  #define DEFINE_VIRTIO_BLK_FEATURES(_state, _field) \
>> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
>> index 5e6e09e..2a3d86f 100644
>> --- a/hw/virtio-pci.c
>> +++ b/hw/virtio-pci.c
>> @@ -886,6 +886,7 @@ static Property virtio_blk_properties[] = {
>>  #ifdef __linux__
>>      DEFINE_PROP_BIT("scsi", VirtIOPCIProxy, blk.scsi, 0, true),
>>  #endif
>> +    DEFINE_PROP_BIT("config-wce", VirtIOPCIProxy, blk.config_wce, 0, true),
>>      DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
>>      DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
>>      DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features),
>>
>
> Could/should this be added to DEFINE_VIRTIO_BLK_FEATURES instead?  You
> don't need the new field, and virtio_blk_get_features can simply omit
> VIRTIO_BLK_F_CONFIG_WCE.  At least that's how virtio-net does it.
>
> It can be done in 1.3 though.

Sounds nice, will send a patch for 1.3.  No user-visible change.

Stefan