Re: [Xen-devel] [PATCH v2 1/4] x86/dom0: prevent access to MMCFG areas for PVH Dom0

[Chao Gao <chao.gao@xxxxxxxxx>]

On Thu, Aug 31, 2017 at 10:03:19AM +0100, Roger Pau Monne wrote:
>On Thu, Aug 31, 2017 at 03:32:42PM +0800, Chao Gao wrote:
>> On Tue, Aug 29, 2017 at 08:33:25AM +0100, Roger Pau Monne wrote:
>> >On Mon, Aug 28, 2017 at 06:18:13AM +0000, Tian, Kevin wrote:
>> >> > From: Roger Pau Monne [mailto:roger.pau@xxxxxxxxxx]
>> >> > Sent: Friday, August 25, 2017 9:59 PM
>> >> > 
>> >> > On Fri, Aug 25, 2017 at 06:25:36AM -0600, Jan Beulich wrote:
>> >> > > >>> On 25.08.17 at 14:15, <roger.pau@xxxxxxxxxx> wrote:
>> >> > > > On Wed, Aug 23, 2017 at 02:16:38AM -0600, Jan Beulich wrote:
>> >> > > >> >>> On 22.08.17 at 15:54, <roger.pau@xxxxxxxxxx> wrote:
>> >> > > >> > On Tue, Aug 22, 2017 at 06:26:23AM -0600, Jan Beulich wrote:
>> >> > > >> >> >>> On 11.08.17 at 18:43, <roger.pau@xxxxxxxxxx> wrote:
>> >> > > >> >> > --- a/xen/arch/x86/dom0_build.c
>> >> > > >> >> > +++ b/xen/arch/x86/dom0_build.c
>> >> > > >> >> > @@ -440,6 +440,10 @@ int __init
>> >> > dom0_setup_permissions(struct domain *d)
>> >> > > >> >> >              rc |= rangeset_add_singleton(mmio_ro_ranges, 
>> >> > > >> >> > mfn);
>> >> > > >> >> >      }
>> >> > > >> >> >
>> >> > > >> >> > +    /* For PVH prevent access to the MMCFG areas. */
>> >> > > >> >> > +    if ( dom0_pvh )
>> >> > > >> >> > +        rc |= pci_mmcfg_set_domain_permissions(d);
>> >> > > >> >>
>> >> > > >> >> What about ones reported by Dom0 later on? Which then raises the
>> >> > > >> >> question whether ...
>> >> > > >> >
>> >> > > >> > This should be dealt with in the PHYSDEVOP_pci_mmcfg_reserved
>> >> > handler.
>> >> > > >> > But since you propose to do white listing, I guess it doesn't 
>> >> > > >> > matter
>> >> > > >> > that much anymore.
>> >> > > >>
>> >> > > >> Well, a fundamental question is whether white listing would work in
>> >> > > >> the first place. I could see room for severe problems e.g. with 
>> >> > > >> ACPI
>> >> > > >> methods wanting to access MMIO that's not described by any PCI
>> >> > > >> devices' BARs. Typically that would be regions in the chipset which
>> >> > > >> firmware is responsible for configuring/managing, the addresses of
>> >> > > >> which can be found/set in custom config space registers.
>> >> > > >
>> >> > > > The question would also be what would Xen allow in such 
>> >> > > > white-listing.
>> >> > > > Obviously you can get to map the same using both white-list and
>> >> > > > black-listing (see below).
>> >> > >
>> >> > > Not really - what you've said there regarding MMCFG regions is
>> >> > > a clear indication that we should _not_ map reserved regions, i.e.
>> >> > > it would need to be full white listing with perhaps just the PCI
>> >> > > device BARs being handled automatically.
>> >> > 
>> >> > I've tried just mapping the BARs and that sadly doesn't work, the box
>> >> > hangs after the IOMMU is enabled:
>> >> > 
>> >> > [...]
>> >> > (XEN) [VT-D]d0:PCI: map 0000:3f:13.5
>> >> > (XEN) [VT-D]d0:PCI: map 0000:3f:13.6
>> >> > (XEN) [VT-D]iommu_enable_translation: iommu->reg = ffff82c00021b000
>> >> > 
>> >> > I will park this ATM and leave it for the Intel guys to diagnose.
>> >> > 
>> >> > For the reference, the specific box I'm testing ATM has a Xeon(R) CPU
>> >> > E5-1607 0 @ 3.00GHz and a C600/X79 chipset.
>> >> > 
>> >> 
>> >> +Chao who can help check whether we have such a box at hand.
>> >> 
>> >> btw please also give your BIOS version.
>> >
>> >It's a Precision T3600 BIOS A14.
>> 
>> Hi, Roger.
>> 
>> I found a Ivy bridge box with E5-2697 v2 and tested with "dom0=pvh", and
>
>The ones I've seen issues with are Sandy Bridge or Nehalem, can you
>find some of this hardware?

As I expected, I was removed from recipents :(, which made me
hard to notice your replies in time. 

Yes. I will. But may take some time (for even Ivy Bridge is rare).

>
>I haven't tested Ivy Bridge, but all Haswell boxes I've tested seem to
>work just fine.

The reason why I chose Ivy Bridge partly is you said you found this bug on
almost pre-haswell box.

Thanks
Chao

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