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

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> 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.

Thanks
kevin

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