Re: [Qemu-devel] [PATCH] VirtIO: Fix QEMU crash during Windows PNP tests

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Mar 02, 2010 at 12:03:15PM +0100, Alexander Graf wrote:
> 
> On 02.03.2010, at 11:09, Michael S. Tsirkin wrote:
> 
> > On Mon, Mar 01, 2010 at 01:26:37PM +0200, Gleb Natapov wrote:
> >> On Mon, Mar 01, 2010 at 12:14:43PM +0100, Alexander Graf wrote:
> >>> 
> >>> On 14.09.2009, at 15:31, Yan Vugenfirer wrote:
> >>> 
> >>>> Signed-off-by: Yan Vugenfirer <yvugenfi@redhat.com>
> >>>> 
> >>>> ---
> >>>> hw/virtio-pci.c |   14 ++++++++++++--
> >>>> 1 files changed, 12 insertions(+), 2 deletions(-)
> >>>> 
> >>>> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> >>>> index f812ab7..a0a22c4 100644
> >>>> --- a/hw/virtio-pci.c
> >>>> +++ b/hw/virtio-pci.c
> >>>> @@ -364,8 +364,17 @@ static void virtio_map(PCIDevice *pci_dev, int region_num,
> >>>> static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
> >>>>                                uint32_t val, int len)
> >>>> {
> >>>> +    VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
> >>>> +
> >>>> +    if (PCI_COMMAND == address) {
> >>>> +        if (!(val & PCI_COMMAND_MASTER)) {
> >>>> +            proxy->vdev->status &= ~VIRTIO_CONFIG_S_DRIVER_OK;
> >>> 
> >>> This part breaks PCI hotplug with Linux guests.
> >>> 
> >>> What happens is the following:
> >> Looks like something is broken even without this patch.
> >> 
> >>> 
> >>> (qemu) pci_add auto nic model=virtio,vlan=0
> >>>  - Virtio dev 1 -> write config (0)
> >>>  - Virtio dev 1 -> write config (0x3)
> >>>  - Virtio dev 1 -> set status explicitly to OK
> >> Why Linux doesn't enable bus mastering on this device?
> > 
> > I fixed this, and Rusty said he has applied the patch,
> > but it seems the patch got lost later:
> > 
> > http://lkml.org/lkml/2009/11/29/73
> > 
> > Alexander, could you please check whether applying
> > this patch fixes hotplug for you?
> > If yes I will queue it up for 2.6.34.
> 
> So we're looking at a guest bug?

Donnu. Does it work with the patch applied?

> It's still a qemu regression then. This configuration used to work
> with 0.10. There should at least be a feature bit from the guest
> saying "I'm good with bus mastering", so we can enable the check only
> for those.
> Alex