Re: [PATCH] pci-assign: Do not reset the device unless the kernel supports it

Avi Kivity
2011-06-07T08:06:58Z

On 06/07/2011 01:04 AM, Jan Kiszka wrote:
> On 2011-06-06 23:48, Alex Williamson wrote:
> > On Mon, 2011-06-06 at 23:30 +0200, Jan Kiszka wrote:
> >> From: Jan Kiszka<jan.kiszka@siemens.com>
> >>
> >> At least kernels 2.6.38 and 2.6.39 do not properly support issuing a
> >> reset on an assigned device and corrupt its config space. Prevent
> >> this by checking for a host kernel with the required support, tagged by
> >> the to-be-introduced KVM_CAP_DEVICE_RESET.
> >
> > Wouldn't it be easier just to revert ed78661f in 2.6.39 stable? I guess
> > we don't have an option to do that for .38 since stable is done there,
> > but there are also some intel-iommu breakages that won't make stable for
> > that release. It seems like the userspace invoked reset resolves known,
> > demonstrable issues of devices continuing to DMA into guest memory while
> > ed78661f is mostly a theoretical change.
>
> Easier would be this patch. But I don't mind reverting the problematic
> commit in 39, whatever is preferred. We should just resolve the issue
> finally.

Kernel problems should be solved in the kernel (with exceptions of
course, but don't see the need here).

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.