linux-kernel - Re: [PATCH 5.10 005/289] KVM: x86/mmu: Remove the defunct update

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Message-ID: <02d72616-2e95-f6cd-403c-60d5f2dfb3f1@redhat.com>
Date:   Thu, 20 May 2021 11:57:48 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Pavel Machek <pavel@...x.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Yu Zhang <yu.c.zhang@...el.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH 5.10 005/289] KVM: x86/mmu: Remove the defunct
 update_pte() paging hook

On 19/05/21 21:56, Pavel Machek wrote:
> Hi!
> 
>> From: Sean Christopherson <seanjc@...gle.com>
>>
>> commit c5e2184d1544f9e56140791eff1a351bea2e63b9 upstream.
>>
>> Remove the update_pte() shadow paging logic, which was obsoleted by
>> commit 4731d4c7a077 ("KVM: MMU: out of sync shadow core"), but never
>> removed.  As pointed out by Yu, KVM never write protects leaf page
> 
> First, this is cleanup, not a bugfix.

It was reported to also fix a bug.  Commit 4731d4c7a077 is 2008 vintage, 
so it is certainly in 5.10.

Paolo

> Second, AFAICT 4731d4c7a077 ("KVM: MMU: out of sync shadow core") is
> not in 5.10, so this will break stuff according to the changelog.