Re: [PATCH 1/4] KVM: MMU: fix permission_fault()

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On 03/30/2016 04:09 AM, Paolo Bonzini wrote:


On 29/03/2016 19:43, Xiao Guangrong wrote:
Based on the SDM:
PK flag (bit 5).
This flag is 1 if (1) IA32_EFER.LMA = CR4.PKE = 1; (2) the access
causing the page-fault exception was a data access; (3) the linear
address was a user-mode address with protection key i; and (5) the PKRU
register (see Section 4.6.2) is such that either (a) ADi = 1; or (b) the
following all hold: (i) WDi = 1; (ii) the access is a write access; and
(iii) either CR0.WP = 1 or the access causing the page-fault exception
was a user-mode access.

So I think PKEY check and ordinary check are independent, i.e, PFEC.PKEY
may be set even if the on permission on the page table is not adequate.

x86/access.flat is currently using the "other" definition, i.e., PFEC.PK
is only set if W=1 or CR0.WP=0 && PFEC.U=0 or PFEC.W=0.  Can you use it
(with ept=1 of course) to check what the processor is doing?


Sure.

And ept=1 is hard to trigger MMU issue, i am enabling PKEY on shadow
MMU, let's see what will happen. ;)
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