Il 17/08/2012 21:25, Kevin Wolf ha scritto: > From: Stefan Hajnoczi <stefa...@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 <pbonz...@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 <pbonz...@redhat.com> > Signed-off-by: Kevin Wolf <kw...@redhat.com> > > Anthony Liguori <aligu...@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 <aligu...@us.ibm.com> > Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com> > Signed-off-by: Kevin Wolf <kw...@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