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

[Xiao Guangrong]

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. ;)