From: Sean Christopherson <seanjc@google.com>
To: Xin Li <xin@zytor.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-pm@vger.kernel.org, pbonzini@redhat.com,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
rafael@kernel.org, pavel@kernel.org, brgerst@gmail.com,
david.kaplan@amd.com, peterz@infradead.org,
andrew.cooper3@citrix.com, kprateek.nayak@amd.com,
arjan@linux.intel.com, chao.gao@intel.com,
rick.p.edgecombe@intel.com, dan.j.williams@intel.com
Subject: Re: [RFC PATCH v1 5/5] KVM: Remove kvm_rebooting and its references
Date: Wed, 17 Sep 2025 16:02:11 -0700 [thread overview]
Message-ID: <aMs986QHpDqk-MSR@google.com> (raw)
In-Reply-To: <e0ce7a92-f8e4-406c-a7dd-c59c8d541d0b@zytor.com>
On Wed, Sep 17, 2025, Xin Li wrote:
> On 9/16/2025 10:56 AM, Sean Christopherson wrote:
> > On Tue, Sep 09, 2025, Xin Li (Intel) wrote:
> > > Drop kvm_rebooting and all related uses. Virtualization is now disabled
> > > immediately before a CPU shuts down, eliminating any chance of executing
> > > virtualization instructions during reboot.
> >
> > Wrong. KVM clears EFER.SVME in reponse to kvm_shutdown(), and thus can trip
> > #UDs on e.g. VMRUN.
> >
>
> This patch assumes that AMD SVM enable/disable has been moved to the CPU
Ah, that wasn't exactly obvious.
> startup and shutdown routines. Accordingly, kvm_shutdown() no longer clears
> EFER.SVME, and the patch demonstrates the resulting simplification from
> removing kvm_rebooting. However, as noted in the cover letter, no actual
> modifications were made to AMD SVM.
Heh, yeah, that's what's wrong.
next prev parent reply other threads:[~2025-09-17 23:02 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 18:28 [RFC PATCH v1 0/5] x86/boot, KVM: Move VMXON/VMXOFF handling from KVM to CPU lifecycle Xin Li (Intel)
2025-09-09 18:28 ` [RFC PATCH v1 1/5] x86/boot: Shift VMXON from KVM init to CPU startup phase Xin Li (Intel)
2025-09-10 5:37 ` Adrian Hunter
2025-09-10 7:25 ` Chao Gao
2025-09-11 6:57 ` Xin Li
2025-09-10 8:02 ` Huang, Kai
2025-09-10 11:10 ` Chao Gao
2025-09-10 11:35 ` Huang, Kai
2025-09-10 13:13 ` Arjan van de Ven
2025-09-10 20:52 ` Huang, Kai
2025-09-09 18:28 ` [RFC PATCH v1 2/5] x86/boot: Move VMXOFF from KVM teardown to CPU shutdown phase Xin Li (Intel)
2025-09-09 18:28 ` [RFC PATCH v1 3/5] x86/shutdown, KVM: VMX: Move VMCLEAR of VMCSs to cpu_disable_virtualization() Xin Li (Intel)
2025-09-09 18:28 ` [RFC PATCH v1 4/5] x86/reboot: Remove emergency_reboot_disable_virtualization() Xin Li (Intel)
2025-09-09 18:28 ` [RFC PATCH v1 5/5] KVM: Remove kvm_rebooting and its references Xin Li (Intel)
2025-09-16 17:56 ` Sean Christopherson
2025-09-17 16:51 ` Xin Li
2025-09-17 23:02 ` Sean Christopherson [this message]
2025-09-11 14:20 ` [RFC PATCH v1 0/5] x86/boot, KVM: Move VMXON/VMXOFF handling from KVM to CPU lifecycle Sean Christopherson
2025-09-11 15:20 ` Dave Hansen
2025-09-16 17:29 ` Sean Christopherson
2025-09-11 17:04 ` Arjan van de Ven
2025-09-16 17:54 ` Sean Christopherson
2025-09-16 18:25 ` Jim Mattson
2025-09-17 13:48 ` Arjan van de Ven
2025-09-17 17:30 ` Xin Li
2025-09-17 22:40 ` Sean Christopherson
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