On Tue, Oct 21, 2014 at 01:35:39PM +0200, Alexander Graf wrote: > > > On 21.10.14 12:16, Michael S. Tsirkin wrote: > > On Mon, Oct 20, 2014 at 06:08:56PM +0200, Alexander Graf wrote: > >> > >> > >> On 20.10.14 08:58, Michael S. Tsirkin wrote: > >>> Current support for bus master (clearing OK bit) together with the need to > >>> support guests which do not enable PCI bus mastering, leads to extra > >>> state in > >>> VIRTIO_PCI_FLAG_BUS_MASTER_BUG bit, which isn't robust in case of > >>> cross-version > >>> migration for the case when guests use the device before setting > >>> DRIVER_OK. > >>> > >>> Rip out this code, and replace it: > >>> - Modern QEMU doesn't need VIRTIO_PCI_FLAG_BUS_MASTER_BUG > >>> so just drop it for latest machine type. > >>> - For compat machine types, set PCI_COMMAND if DRIVER_OK > >>> is set. > >>> > >>> As this is needed for 2.1 for both pc and ppc, move PC_COMPAT macros from > >>> pc.h > >>> to a new common header. > >>> > >>> Reviewed-by: Greg Kurz <gk...@linux.vnet.ibm.com> > >>> Tested-by: Greg Kurz <gk...@linux.vnet.ibm.com> > >>> Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > >>> --- > >>> > >>> Alexander, could you pls ack me merging this? > >>> Thanks! > >> > >> Have you tried whether this works with old kernel versions? We > >> introduced the broken flag for very specific old kernel versions that > >> got their flags wrong IIRC. > >> > >> > >> Alex > > > > Yes. The point is that since 2.1 the broken flag isn't effective > > anymore: when bus master is off, PCI blocks outgoing transactions and > > setting internal flags isn't going to help. > > > > Instead, we detect a buggy guest and immediately enable bus master for > > it - no need for a separate flag. > > Ok, works for me then. > > > Alex
cool. Gerd tells me there's a conflict with your next tree: would you like for me to wait until it's merged, or go ahead and send pull request and rebase yours on top? -- MST
