Re: [Xen-devel] [V1 PATCH] PVH: avoid call to handle_mmio

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.06.14 at 00:00, <mukesh.rathor@xxxxxxxxxx> wrote:
> handle_mmio() is currently unsafe for pvh guests. A call to it would
> result in call to vioapic_range that will crash xen since the vioapic
> ptr in struct hvm_domain is not initialized for pvh guests.
> 
> However, one path exists for such a call. If a pvh guest, dom0 or domU,
> unintentionally touches non-existing memory, an EPT violation would occur.
> This would result in unconditional call to hvm_hap_nested_page_fault. In
> that function, because get_gfn_type_access returns p2m_mmio_dm for non
> existing mfns by default, handle_mmio() will get called. This would result
> in xen crash instead of the guest crash. This patch addresses that.

Yes, we definitely want this until being properly handled, no matter
that crashing the guest here doesn't seem to be the right thing either
(normal x86 behavior would be to drop writes and return all ones for
reads).

Jan


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