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Subject: Re: [PATCH v3 2/3] KVM: x86: Move pkru save/restore to x86.c
To:     Babu Moger <babu.moger@amd.com>, Jim Mattson <jmattson@google.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
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From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <6982aaa9-d1ee-db8a-2eeb-6063c9bc342c@redhat.com>
Date:   Wed, 13 May 2020 08:47:07 +0200
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On 12/05/20 19:17, Babu Moger wrote:
> 
> 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.

I will take care of this for v4 (pick this patch up and put it in
5.7-rc, package everything as a topic branch, merge it to kvm/next).

Paolo