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Fri, 07 Aug 2026 08:20:48 +0000 Date: Fri, 07 Aug 2026 09:20:47 +0100 Message-ID: <8633wqbau8.wl-maz@kernel.org> From: Marc Zyngier To: Sean Christopherson Cc: Oliver Upton , Paolo Bonzini , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: Never clear KVM_REQ_VM_DEAD from a vCPU's requests In-Reply-To: <20260806214618.82180-1-seanjc@google.com> References: <20260806214618.82180-1-seanjc@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: seanjc@google.com, oupton@kernel.org, pbonzini@redhat.com, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 06 Aug 2026 22:46:18 +0100, Sean Christopherson wrote: > > Use kvm_test_request() instead of kvm_check_request() when querying > KVM_REQ_VM_DEAD, i.e. don't clear KVM_REQ_VM_DEAD, as the entire purpose > of KVM_REQ_VM_DEAD is to prevent the vCPU from enterring the guest ever > again, even if userspace insists on redoing KVM_RUN. > > Ensuring KVM_REQ_VM_DEAD is never cleared will allow relaxing KVM's rule > that ioctls can't be invoked on dead VMs, to only disallow ioctls if the > VM is bugged, i.e. if KVM hit a KVM_BUG_ON(). > > Opportunistically add compile-time assertions to guard against clearing > KVM_REQ_VM_DEAD through the standard APIs. > > Signed-off-by: Sean Christopherson Acked-by: Marc Zyngier M. -- Without deviation from the norm, progress is not possible.