linux-kernel - Re: [PATCH] KVM: x86/mmu: Guard against collision with KVM-defined PFERR_IMPLICIT

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Message-ID: <169101966149.1829182.8699224723247011152.b4-ty@google.com>
Date:   Wed,  2 Aug 2023 17:04:59 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86/mmu: Guard against collision with KVM-defined PFERR_IMPLICIT_ACCESS

On Fri, 21 Jul 2023 15:37:11 -0700, Sean Christopherson wrote:
> Add an assertion in kvm_mmu_page_fault() to ensure the error code provided
> by hardware doesn't conflict with KVM's software-defined IMPLICIT_ACCESS
> flag.  In the unlikely scenario that future hardware starts using bit 48
> for a hardware-defined flag, preserving the bit could result in KVM
> incorrectly interpreting the unknown flag as KVM's IMPLICIT_ACCESS flag.
> 
> WARN so that any such conflict can be surfaced to KVM developers and
> resolved, but otherwise ignore the bit as KVM can't possibly rely on a
> flag it knows nothing about.
> 
> [...]

Applied to kvm-x86 mmu, thanks!

[1/1] KVM: x86/mmu: Guard against collision with KVM-defined PFERR_IMPLICIT_ACCESS
      https://github.com/kvm-x86/linux/commit/3e90c27b4209

--
https://github.com/kvm-x86/linux/tree/next
https://github.com/kvm-x86/linux/tree/fixes