PCI hotplug broken?

PCI hotplug broken?

[Alexander Graf]

Hi list,

While trying to upgrade some internal infrastructure to qemu-kvm-0.12 I stumbled across this really weird problem that I see with current qemu-kvm git too:

I start qemu-kvm using:

./qemu-system-x86_64 -L ../pc-bios/ -m 512 -net nic,model=virtio -net tap,ifname=tap0,script=/bin/true -snapshot sles11.qcow2 -vnc :0 -monitor stdio

The system boots up just fine, networking works.

On the qemu monitor I then issue:

(qemu) pci_add auto storage file=/tmp/image.raw,if=virtio

after which I get a fully functional virtio block device, but the network stops sending/receiving packets.

The same thing with qemu-kvm-0.10 works just fine. Has anyone seen this before?


Alex

Re: PCI hotplug broken?

[Alexander Graf]

On 26.02.2010, at 15:12, Alexander Graf wrote:

> Hi list,
> 
> While trying to upgrade some internal infrastructure to qemu-kvm-0.12 I stumbled across this really weird problem that I see with current qemu-kvm git too:
> 
> I start qemu-kvm using:
> 
> ./qemu-system-x86_64 -L ../pc-bios/ -m 512 -net nic,model=virtio -net tap,ifname=tap0,script=/bin/true -snapshot sles11.qcow2 -vnc :0 -monitor stdio
> 
> The system boots up just fine, networking works.
> 
> On the qemu monitor I then issue:
> 
> (qemu) pci_add auto storage file=/tmp/image.raw,if=virtio
> 
> after which I get a fully functional virtio block device, but the network stops sending/receiving packets.
> 
> The same thing with qemu-kvm-0.10 works just fine. Has anyone seen this before?

Same thing happens when hotplug only:

pci_add auto nic model=virtio,vlan=0

-> network works

pci_add auto storage file=/tmp/image.raw,if=virtio

-> network stops working

pci_add auto nic model=virtio,vlan=0

-> network works again on the new device


Alex

Re: PCI hotplug broken?

[Marcelo Tosatti]

On Fri, Feb 26, 2010 at 03:53:48PM +0100, Alexander Graf wrote:
> 
> On 26.02.2010, at 15:12, Alexander Graf wrote:
> 
> > Hi list,
> > 
> > While trying to upgrade some internal infrastructure to qemu-kvm-0.12 I stumbled across this really weird problem that I see with current qemu-kvm git too:
> > 
> > I start qemu-kvm using:
> > 
> > ./qemu-system-x86_64 -L ../pc-bios/ -m 512 -net nic,model=virtio -net tap,ifname=tap0,script=/bin/true -snapshot sles11.qcow2 -vnc :0 -monitor stdio
> > 
> > The system boots up just fine, networking works.
> > 
> > On the qemu monitor I then issue:
> > 
> > (qemu) pci_add auto storage file=/tmp/image.raw,if=virtio
> > 
> > after which I get a fully functional virtio block device, but the network stops sending/receiving packets.
> > 
> > The same thing with qemu-kvm-0.10 works just fine. Has anyone seen this before?
> 
> Same thing happens when hotplug only:
> 
> pci_add auto nic model=virtio,vlan=0
> 
> -> network works
> 
> pci_add auto storage file=/tmp/image.raw,if=virtio
> 
> -> network stops working
> 
> pci_add auto nic model=virtio,vlan=0
> 
> -> network works again on the new device

Can reproduce it. "info pci" shows IRQ0 assigned to virtio-blk.
Did you try, say, e1000 and SCSI ?

Re: PCI hotplug broken?

[Alexander Graf]

On 01.03.2010, at 18:51, Marcelo Tosatti wrote:

> On Fri, Feb 26, 2010 at 03:53:48PM +0100, Alexander Graf wrote:
>> 
>> On 26.02.2010, at 15:12, Alexander Graf wrote:
>> 
>>> Hi list,
>>> 
>>> While trying to upgrade some internal infrastructure to qemu-kvm-0.12 I stumbled across this really weird problem that I see with current qemu-kvm git too:
>>> 
>>> I start qemu-kvm using:
>>> 
>>> ./qemu-system-x86_64 -L ../pc-bios/ -m 512 -net nic,model=virtio -net tap,ifname=tap0,script=/bin/true -snapshot sles11.qcow2 -vnc :0 -monitor stdio
>>> 
>>> The system boots up just fine, networking works.
>>> 
>>> On the qemu monitor I then issue:
>>> 
>>> (qemu) pci_add auto storage file=/tmp/image.raw,if=virtio
>>> 
>>> after which I get a fully functional virtio block device, but the network stops sending/receiving packets.
>>> 
>>> The same thing with qemu-kvm-0.10 works just fine. Has anyone seen this before?
>> 
>> Same thing happens when hotplug only:
>> 
>> pci_add auto nic model=virtio,vlan=0
>> 
>> -> network works
>> 
>> pci_add auto storage file=/tmp/image.raw,if=virtio
>> 
>> -> network stops working
>> 
>> pci_add auto nic model=virtio,vlan=0
>> 
>> -> network works again on the new device
> 
> Can reproduce it. "info pci" shows IRQ0 assigned to virtio-blk.
> Did you try, say, e1000 and SCSI ?

I just sent a reply to qemu-devel today (Re: [Qemu-devel] [PATCH] VirtIO: Fix QEMU crash during Windows PNP tests) explaining what is broken.

So no, it seems to be a virtio issue. I really have no idea why bus mastering doesn't get enabled though.

Alex