On 21.10.14 14:10, Michael S. Tsirkin wrote: > 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?
Whoever sends it first wins I'd say ;) Alex
