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Subject: Re: [PATCH v3 2/3] KVM: x86: Move pkru save/restore to x86.c
To:     Jim Mattson <jmattson@google.com>
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From:   Babu Moger <babu.moger@amd.com>
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Date:   Tue, 12 May 2020 12:17:59 -0500
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On 5/12/20 11:39 AM, Jim Mattson wrote:
> On Mon, May 11, 2020 at 4:33 PM Babu Moger <babu.moger@amd.com> wrote:
>>
>> MPK feature is supported by both VMX and SVM. So we can
>> safely move pkru state save/restore to common code. Also
>> move all the pkru data structure to kvm_vcpu_arch.
>>
>> Also fixes the problem Jim Mattson pointed and suggested below.
>>
>> "Though rdpkru and wrpkru are contingent upon CR4.PKE, the PKRU
>> resource isn't. It can be read with XSAVE and written with XRSTOR.
>> So, if we don't set the guest PKRU value here(kvm_load_guest_xsave_state),
>> the guest can read the host value.
>>
>> In case of kvm_load_host_xsave_state, guest with CR4.PKE clear could
>> potentially use XRSTOR to change the host PKRU value"
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
> 
> I would do the bugfix as a separate commit, to ease backporting it to
> the stable branches.

Ok. Sure.