linux-kernel - Re: [PATCH v3] KVM: x86/mmu: Warn on iTLB multi-hit for possible problems

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] [day] [month] [year] [list]

Message-ID: <YbD8KFaY+emLQR+d@google.com>
Date:   Wed, 8 Dec 2021 18:40:40 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Li Yu <liyu.yukiteru@...edance.com>
Cc:     pbonzini@...hat.com, Jonathan Corbet <corbet@....net>,
        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>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        Muchun Song <songmuchun@...edance.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Robin Murphy <robin.murphy@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v3] KVM: x86/mmu: Warn on iTLB multi-hit for possible
 problems

On Wed, Oct 20, 2021, Li Yu wrote:
> Warn for guest huge pages split if iTLB multi-hit bug is present
> and CPU mitigations is enabled.
> 
> Warn for possible CPU lockup if iTLB multi-hit bug is present but
> CPU mitigations is disabled.
> 
> Signed-off-by: Li Yu <liyu.yukiteru@...edance.com>
> ---

Gah, my last reply in the previous version was offlist.  I would like an answer
to the below question before we complicate KVM just to log a message.

On Wed, Oct 20, 2021 at 12:51 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Wed, Oct 20, 2021, Li Yu wrote:
> > On 2021/10/20 00:23, Sean Christopherson wrote:
> > I think it is necessary to log something when `nx_huge_pages` is `auto` or
> > `off`, and the bug is present.
>
> Why is it necessary?  Specifically, what action can be taken based on KVM logging
> that can't reasonably be taken based on all the other information provided by the
> kernel?  We should teach userspace to go look at the vulnerabilites info, not to
> scrape the kernel log.