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

[Alexander Graf]

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 <address@hidden>
>>>> 
>>>> ---
>>>> 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?

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