Subject: Re: [PATCH 1/4] KVM: MMU: fix permission_fault()
To: Paolo Bonzini <pbonzini@redhat.com>
References: <1458911978-19430-1-git-send-email-guangrong.xiao@linux.intel.com>
 <56F54983.4010508@redhat.com> <56FABECE.40601@linux.intel.com>
 <56FAE0F3.9090809@redhat.com>
Cc: gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Message-ID: <56FB3254.5070403@linux.intel.com>
Date: Wed, 30 Mar 2016 09:56:36 +0800
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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. ;)