virtio-blk: hide VIRTIO_BLK_F_CONFIG_WCE from old machine types
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>
projects / sdk / emulator / qemu.git / commit