Re: [PATCH v2] kvm: Disable MSI/MSI-X in assigned device reset path

[Avi Kivity <avi@redhat.com>]

On 04/08/2012 08:37 PM, Jan Kiszka wrote:
> The core problem is not the ordering. The problem is that the kernel is
> susceptible to ordering mistakes of userspace. And that is because the
> kernel panics on PCI errors of devices that are in user hands - a
> critical kernel bug IMHO. 

Certainly.  But this userspace patch won't fix it.

> Proper reset of MSI or even the whole PCI
> config space is another issue, but one the kernel should not worry about
> - still, it should be fixed (therefore this patch).

And I was asking what is the right way to do it.  Reset the device and
read back the register values, or do an emulated reset and push down the
register values.

> But even if we disallowed userland to disable MMIO and PIO access to the
> device, we would be be able to exclude that there are secrete channels
> in the device's interface having the same effect. So we likely need to
> enhance PCI error handling to catch and handle faults for certain
> devices differently - those we cannot trust to behave properly while
> they are under userland/guest control.

Why not all of them?

-- 
error compiling committee.c: too many arguments to function