linux-kernel - Re: [PATCH] KVM: MMU: shadow nested paging does not have PKU

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Date:   Mon, 29 Nov 2021 13:08:22 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     stable@...r.kernel.org
Subject: Re: [PATCH] KVM: MMU: shadow nested paging does not have PKU

On 11/27/21 4:25 AM, Paolo Bonzini wrote:
> On 11/27/21 02:21, Lai Jiangshan wrote:
>>
>>
>> On 2021/11/26 21:21, Paolo Bonzini wrote:
>>> Initialize the mask for PKU permissions as if CR4.PKE=0, avoiding
>>> incorrect interpretations of the nested hypervisor's page tables.
>>
>> I think the AMD64 volume2 Architecture Programmer’s Manual does not
>> specify it, but it seems that for a sane NPT walk, PKU should not work
>> in NPT.
> 
> The PK bit is not defined in the nested page fault EXITINFO1, too. Thomas, 
> can you have it fixed in the APM that the host's SMEP, SMAP and PKE bits 
> do not affect nested page table walks?
> 

I talked to our documentation folks and they will look to update the APM 
with the appropriate information.

Thanks,
Tom