linux-kernel - Re: [PATCH 15/15] KVM: X86: Always set gpte_is_8

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Message-ID: <65e1f2ca-5d89-d67f-2e0e-542094f89f05@redhat.com>
Date:   Thu, 18 Nov 2021 16:01:25 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Lai Jiangshan <laijs@...ux.alibaba.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH 15/15] KVM: X86: Always set gpte_is_8_bytes when direct
 map

On 11/18/21 15:34, Lai Jiangshan wrote:
> 
> 
> On 2021/11/18 19:12, Paolo Bonzini wrote:
>> On 11/18/21 12:08, Lai Jiangshan wrote:
>>> From: Lai Jiangshan <laijs@...ux.alibaba.com>
>>>
>>> When direct map, gpte_is_8_bytes has no meaning, but it is true for all
>>> other cases except direct map when nonpaping.
>>>
>>> Setting gpte_is_8_bytes to true when nonpaping can ensure that
>>> !gpte_is_8_bytes means 32-bit gptes for shadow paging.
>>
>> Then the right thing to do would be to rename it to has_4_byte_gptes 
>> and invert the direction.  But as things stand, it's a bit more 
>> confusing to make gpte_is_8_bytes=1 if there are no guest PTEs at all.
>>
> 
> I will make the last 3 patches be a separated patchset and will do the 
> rename.

Patches 13 and 14 are fine actually.

Paolo