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

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

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.


> > 
> > (qemu) pci_add auto storage file=/tmp/image.raw,if=virtio
> >   - Virtio dev 1 -> write config (0x3)
> Why Linux touches unrelated device's config space?
> 
> >   -> Unset DRIVER_OK bit
> >   -> network device becomes unresponsive 
> >   - Virtio dev 2 -> write config (0)
> >   - Virtio dev 2 -> write config (0x3)
> >   - Virtio dev 2 -> set status explicitly to OK
> > 
> > 
> > Please either revert this patch or provide a proper fix.
> > 
> > Alex
> 
> --
> 			Gleb.