Re: [Xen-devel] [PATCH v3 10/10] x86/MSI-X: provide hypercall interface for mask-all control

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.06.15 at 16:07, <roger.pau@xxxxxxxxxx> wrote:
> I don't mind adding a PHYSDEVOP_pci_mmcfg_reserved call to FreeBSD, but
> for it to have any effect we need to stop unconditionally mapping
> everything as MMIO regions on PVH Dom0.

Actually I don't think we need this as a prereq (it's rather a pretty
orthogonal change, which I nevertheless agree should be carried
out soon): Even if the kernel registered the MMCFG ranges,
whether it maps them up front could be of no interest to Xen in
the PVH case (in the PV case we'd need to search for mappings in
page tables, so we wouldn't want to lift the ordering restriction).
Xen could deal with the permission change in two ways: For one,
MMIO ranges are 1:1 mapped, so it could brute force adjust the
affected 2nd level paging entries. Alternatively we could (ab)use
p2m_mmio_write_dm for the Dom0 case, and invoke
p2m_change_entry_type_global(d, p2m_mmio_direct,
p2m_mmio_write_dm) upon registration of an MMCFG range.

Jan


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