linux-kernel - Re: [PATCH 1/4] KVM: MMU: fix permission

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Message-ID: <56FAE0F3.9090809@redhat.com>
Date:	Tue, 29 Mar 2016 22:09:23 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Cc:	gleb@...nel.org, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] KVM: MMU: fix permission_fault()



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?

Paolo