From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Yosry Ahmed <yosry@kernel.org>
Subject: Re: [PATCH v2 0/2] KVM: x86: Syzkaller nested_run_pending defense
Date: Tue, 7 Apr 2026 17:14:36 -0700 [thread overview]
Message-ID: <177560706203.1572452.5325835766446538096.b4-ty@google.com> (raw)
In-Reply-To: <20260312234823.3120658-1-seanjc@google.com>
On Thu, 12 Mar 2026 16:48:21 -0700, Sean Christopherson wrote:
> Stop playing a losing game of whack-a-mole with syzkaller over
> nested_run_pending, and simply treat the flag as "untrusted" if userspace gains
> control of the vCPU. I.e. don't WARN if userspace _may_ have stuffed vCPU
> state to force an impossible VM-Exit.
>
> The signal:noise ratio for nested_run_pending WARNs when syzkaller is fuzzing
> nVMX/nSVM is awful, and playing whack-a-mole with syzkaller is doing more harm
> that good at this point. While it's possible syzkaller could find an actual
> KVM bug by stuffing vCPU state, if the _only_ symptom is the nested_run_pending
> WARN, then in theory the bug should also be hittable by stuffing L2 state prior
> to nested VM-Enter.
>
> [...]
Applied to kvm-x86 nested.
[1/2] KVM: x86: Move nested_run_pending to kvm_vcpu_arch
https://github.com/kvm-x86/linux/commit/3d4470d71fbf
[2/2] KVM: x86: Suppress WARNs on nested_run_pending after userspace exit
https://github.com/kvm-x86/linux/commit/7212094baef5
--
https://github.com/kvm-x86/linux/tree/next
prev parent reply other threads:[~2026-04-08 0:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-12 23:48 Sean Christopherson
2026-03-12 23:48 ` [PATCH v2 1/2] KVM: x86: Move nested_run_pending to kvm_vcpu_arch Sean Christopherson
2026-03-12 23:48 ` [PATCH v2 2/2] KVM: x86: Suppress WARNs on nested_run_pending after userspace exit Sean Christopherson
2026-04-08 0:14 ` Sean Christopherson [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=177560706203.1572452.5325835766446538096.b4-ty@google.com \
--to=seanjc@google.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=yosry@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®