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

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

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.

Thanks, Roger.

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