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> <56FB3254.5070403@linux.intel.com>
 <56FB73E0.7060601@redhat.com>
Cc: gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, "Han, Huaitong" <huaitong.han@intel.com>
From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Message-ID: <56FB7489.2080304@linux.intel.com>
Date: Wed, 30 Mar 2016 14:39:05 +0800
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On 03/30/2016 02:36 PM, Paolo Bonzini wrote:
>
>
> On 30/03/2016 03:56, Xiao Guangrong wrote:
>>> 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. ;)
>
> No, don't do that!
>
> ept=1 lets you test what the processor does.  It means you cannot test
> permission_fault(), but what we want here is just reverse engineering
> the microcode.  ept=1 lets you do exactly that.

Yes, i got this point. Huaitong will do the test once the machine gets
free.