From: "Nikunj A. Dadhania" <nikunj@amd.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: <kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] KVM: x86: Ensure vendor's exit handler runs before fastpath userspace exits
Date: Fri, 24 Apr 2026 09:59:09 +0530 [thread overview]
Message-ID: <5a4a7257-c26b-4173-bdf4-3f08f9cf12b6@amd.com> (raw)
In-Reply-To: <20260423162628.490962-2-seanjc@google.com>
On 4/23/2026 9:56 PM, Sean Christopherson wrote:
> Move the handling of fastpath userspace exits into vendor code to ensure
> KVM runs vendor specific operations that need to run before userspace gains
> control of the vCPU. E.g. for VMX (and soon to be for SVM as well), KVM
> needs to flush the PML buffer prior to exiting to userspace, otherwise any
> memory written by the final KVM_RUN might never be flagged as dirty.
>
> Note, waiting to snapshot CR0 and CR3 until svm_handle_exit() is flawed in
> general, as that risks consuming stale state in a fastpath handler. That
> will be addressed in a future change.
>
> Fixes: f7f39c50edb9 ("KVM: x86: Exit to userspace if fastpath triggers one on instruction skip")
> Cc: stable@vger.kernel.org
> Cc: Nikunj A. Dadhania <nikunj@amd.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Nikunj A. Dadhania <nikunj@amd.com>
next prev parent reply other threads:[~2026-04-24 4:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-23 16:26 [PATCH 0/2] KVM: x86: Fastpath userspace exit fix and hardening Sean Christopherson
2026-04-23 16:26 ` [PATCH 1/2] KVM: x86: Ensure vendor's exit handler runs before fastpath userspace exits Sean Christopherson
2026-04-23 21:48 ` Huang, Kai
2026-04-24 4:29 ` Nikunj A. Dadhania [this message]
2026-04-23 16:26 ` [PATCH 2/2] KVM: SVM: Refresh vcpu->arch.cr{0,3} prior to invoking fastpath handler Sean Christopherson
2026-04-24 8:45 ` Nikunj A. Dadhania
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