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Subject: Re: [PATCH] KVM: x86: add hint to skip hidden rdpkru under
 kvm_load_host_xsave_state
To:     Dave Hansen <dave.hansen@intel.com>,
        Andy Lutomirski <luto@kernel.org>, Jon Kohler <jon@nutanix.com>
Cc:     Babu Moger <babu.moger@amd.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
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        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Yu-cheng Yu <yu-cheng.yu@intel.com>,
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        Uros Bizjak <ubizjak@gmail.com>,
        Petteri Aimonen <jpa@git.mail.kapsi.fi>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Fan Yang <Fan_Yang@sjtu.edu.cn>,
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        Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
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From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <e8033c48-86aa-397b-57aa-71d65d834e9f@redhat.com>
Date:   Mon, 17 May 2021 18:43:56 +0200
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On 17/05/21 15:54, Dave Hansen wrote:
> On 5/13/21 10:11 PM, Andy Lutomirski wrote:
>> I don't even want to think about what happens if a perf NMI hits and
>> accesses host user memory while the guest PKRU is live (on VMX -- I
>> think this can't happen on SVM).
> 
> What's the relevant difference between SVM and VMX here?  I'm missing
> something.

SVM has the global interrupt flag that blocks NMIs and SMIs, and PKRU is 
loaded while GIF=0.

Paolo