Re: [Xen-devel] Re: [PATCH] re-enable HVM PCI passthrough functionality

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 09:34 +0100 on 02 Sep (1283420058), Christoph Egger wrote:
> On Thursday 02 September 2010 04:26:32 Zhang, Yang Z wrote:
> > With allen's patch, both vt-d and sr-iov can work now. Thanks allen.
> 
> We were not able to reproduce SR-IOV failures with and without the fix
> on AMD machines. I am wondering if there are differences in memory
> mappings between AMD and Intel PCI passthrough.

I expect that you tested on machines with >4GiB of RAM, passing through
32-bit MMIO addresses (which would then pass mfn_valid()) and Intel
either had less RAM or higher BARs in their test (so their MMIO
addresses were !mfn_valid() but != INVALID_MFN).

Cheers,

Tim.

> Nonetheless, good to know this has been fixed.
> 
> Thanks,
> Christoph
> 
> > best regards
> > yang
> >
> > > -----Original Message-----
> > > From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> > > [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Tim Deegan
> > > Sent: Wednesday, September 01, 2010 4:57 PM
> > > To: Kay, Allen M
> > > Cc: Christoph Egger; xen-devel@xxxxxxxxxxxxxxxxxxx; Keir Fraser
> > > Subject: [Xen-devel] Re: [PATCH] re-enable HVM PCI passthrough
> > > functionality
> > >
> > > At 17:13 +0100 on 31 Aug (1283274786), Kay, Allen M wrote:
> > > > I have updated the patch to indicate valid_mfn() cannot be used here
> > > > as MMIO pages are always above max_mem.  Also added sanity checking
> > > > for type == p2m_mmio_direct before clearing page table entry.  This
> > > > should fix both VT-d and SR-IOV issues reported recently as there are
> > > > no SR-IOV specific code in Xen.  As far as Xen is concern, SR-IOV
> > > > virtual function is just another PCI device.
> > >
> > > Applied; thanks for the fix.
> > >
> > > Tim.
> > >
> > > > Signed-off-by: Allen Kay allen.m.kay@xxxxxxxxx
> > > >
> > > > -----Original Message-----
> > > > From: Christoph Egger [mailto:Christoph.Egger@xxxxxxx]
> > > > Sent: Tuesday, August 31, 2010 2:35 AM
> > > > To: Tim Deegan
> > > > Cc: Kay, Allen M; xen-devel@xxxxxxxxxxxxxxxxxxx; Keir Fraser
> > > > Subject: Re: [PATCH] re-enable HVM PCI passthrough functionality
> > > >
> > > > On Tuesday 31 August 2010 11:17:27 Tim Deegan wrote:
> > > > > At 02:58 +0100 on 31 Aug (1283223494), Kay, Allen M wrote:
> > > > > > Attached patch reverts back to INVALID_MFN.  PCI passthrough
> > > > > > functionality works with this patch.
> > > > >
> > > > > Apologies for missing this - I did ask for this enormous patch to
> > > > > contain only what it said on the tin (and I did read it to check!)
> > > > > but this one got through.
> > > >
> > > > Also apologies from my side. I did what Tim requested for, but that
> > > > one slipped through.
> > > >
> > > > > > Signed-off-by: Allen Kay allen.m.kay@xxxxxxxxx
> > > > >
> > > > > This is fine, but please add a comment explaining the rather subtle
> > > > > use of INVALID_MFN here so the next tidy-minded person doesn't "fix"
> > > > > it again. :)
> > > > >
> > > > > In fact would it be better to check the returned type ==
> > > > > p2m_mmio_direct instead?  That seems like it would fit better with
> > > > > the intention.   Or do other callers use this to clean non-mmio
> > > > > entries too?
> > > >
> > > > I'm interested in if this patch fixes the SR-IOV issue. We are still
> > > > about investigation...
> > > >
> > > > Christoph
> 
> 
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-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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