linux-kernel - Re: [PATCH 2/2] KVM: x86/mmu: Comment FNAME(sync

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALMp9eQn+QaK630apzOz-L-btHxGQuXcbEiovO8FLOtMmQp_CQ@mail.gmail.com>
Date:   Fri, 13 May 2022 13:27:25 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, David Matlack <dmatlack@...gle.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH 2/2] KVM: x86/mmu: Comment FNAME(sync_page) to document
 TLB flushing logic

On Fri, May 13, 2022 at 12:50 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Add a comment to FNAME(sync_page) to explain why the TLB flushing logic
> conspiculously doesn't handle the scenario of guest protections being
> reduced.  Specifically, if synchronizing a SPTE drops execute protections,
> KVM will not emit a TLB flush, whereas dropping writable or clearing A/D
> bits does trigger a flush via mmu_spte_update().  Architecturally, until
> the GPTE is implicitly or explicitly flushed from the guest's perspective,
> KVM is not required to flush any old, stale translations.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
Reviewed-by: Jim Mattson <jmattson@...gle.com>