[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control o
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register |
Date: |
Sun, 7 Jun 2015 08:23:53 +0200 |
On Mon, Apr 20, 2015 at 04:32:12PM +0200, Michael S. Tsirkin wrote:
> On Mon, Apr 20, 2015 at 03:08:09PM +0100, Jan Beulich wrote:
> > >>> On 20.04.15 at 15:43, <address@hidden> wrote:
> > > On Mon, Apr 13, 2015 at 01:51:06PM +0100, Jan Beulich wrote:
> > >> >>> On 13.04.15 at 14:47, <address@hidden> wrote:
> > >> > Can you check device capabilities register, offset 0x4 within
> > >> > pci express capability structure?
> > >> > Bit 15 is 15 Role-Based Error Reporting.
> > >> > Is it set?
> > >> >
> > >> > The spec says:
> > >> >
> > >> > 15
> > >> > On platforms where robust error handling and PC-compatible
> > >> > Configuration
> > >> > Space probing is
> > >> > required, it is suggested that software or firmware have the
> > >> > Unsupported
> > >> > Request Reporting Enable
> > >> > bit Set for Role-Based Error Reporting Functions, but clear for
> > >> > 1.0a
> > >> > Functions. Software or
> > >> > firmware can distinguish the two classes of Functions by
> > >> > examining the
> > >> > Role-Based Error Reporting
> > >> > bit in the Device Capabilities register.
> > >>
> > >> Yes, that bit is set.
> > >
> > > curiouser and curiouser.
> > >
> > > So with functions that do support Role-Based Error Reporting, we have
> > > this:
> > >
> > >
> > > With device Functions implementing Role-Based Error Reporting, setting
> > > the
> > > Unsupported Request
> > > Reporting Enable bit will not interfere with PC-compatible
> > > Configuration
> > > Space probing, assuming
> > > that the severity for UR is left at its default of non-fatal. However,
> > > setting the Unsupported Request
> > > Reporting Enable bit will enable the Function to report UR errors 97
> > > detected with posted Requests,
> > > helping avoid this case for potential silent data corruption.
> >
> > I still don't see what the PC-compatible config space probing has to
> > do with our issue.
>
> I'm not sure but I think it's listed here because it causes a ton of URs
> when device scan probes unimplemented functions.
>
> > > did firmware reconfigure this device to report URs as fatal errors then?
> >
> > No, the Unsupported Request Error Serverity flag is zero.
> >
> > Jan
>
> OK, that's the correct configuration, so how come the box crashes when
> there's a UR then?
Ping - any update on this?
Do we can chalk this up to hardware bugs on a specific box?
> --
> MST