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Re: [Xen-devel] [PATCH] x86/PCI: Intercept Dom0 MMCFG from dom0s in HVM containers

On 12/17/2015 04:46 AM, Jan Beulich wrote:
On 16.12.15 at 20:34, <boris.ostrovsky@xxxxxxxxxx> wrote:
On 12/16/2015 04:04 AM, Jan Beulich wrote:
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3116,6 +3116,21 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long 
           goto out_put_gfn;
+ if ( (p2mt == p2m_mmio_direct) && is_hardware_domain(currd) )
The PV condition includes a PFEC_page_present check, and I think
an equivalent should be added here too.
Hmm.. So how would I determine that? I can see how this is available in
SVM (although it is not reflected in npfec) but in VMX I don't see
direct indication of whether the page was present.
That's what bits 3..5 of the exit qualification can be used for. Really
you could leverage the more fine grained reporting by EPT to make
the condition here "bit 1 must be set" (i.e. npfec.write_access) and
"bit 3 must be set" (readable, which implies present) and "bit 4 must
be clear" (and we might even demand bit 5 to be clear too).

OK, but these bits are not mapped into npfec structure so we'd need to expand it.

(And then SVM does not provide this much information so we may need to get creative there).


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