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Mon, 24 Feb 2025 15:55:55 -0800 (PST) Reply-To: Sean Christopherson Date: Mon, 24 Feb 2025 15:55:41 -0800 In-Reply-To: <20250224235542.2562848-1-seanjc@google.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Mime-Version: 1.0 References: <20250224235542.2562848-1-seanjc@google.com> X-Mailer: git-send-email 2.48.1.658.g4767266eb4-goog Message-ID: <20250224235542.2562848-7-seanjc@google.com> Subject: [PATCH 6/7] KVM: x86: Fold guts of kvm_arch_sync_events() into kvm_arch_pre_destroy_vm() From: Sean Christopherson To: Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Madhavan Srinivasan , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Sean Christopherson , Paolo Bonzini Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Aaron Lewis , Jim Mattson , Yan Zhao , Rick P Edgecombe , Kai Huang , Isaku Yamahata Content-Type: text/plain; charset="UTF-8" Fold the guts of kvm_arch_sync_events() into kvm_arch_pre_destroy_vm(), as the kvmclock and PIT background workers only need to be stopped before destroying vCPUs (to avoid accessing vCPUs as they are being freed); it's a-ok for them to be running while the VM is visible on the global vm_list. Note, the PIT also needs to be stopped before IRQ routing is freed (because KVM's IRQ routing is garbage and assumes there is always non-NULL routing). Opportunistically add comments to explain why KVM stops/frees certain assets early. Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a61dbd1f0d01..ea445e6579f1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12772,9 +12772,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) void kvm_arch_sync_events(struct kvm *kvm) { - cancel_delayed_work_sync(&kvm->arch.kvmclock_sync_work); - cancel_delayed_work_sync(&kvm->arch.kvmclock_update_work); - kvm_free_pit(kvm); + } /** @@ -12855,6 +12853,17 @@ EXPORT_SYMBOL_GPL(__x86_set_memory_region); void kvm_arch_pre_destroy_vm(struct kvm *kvm) { + /* + * Stop all background workers and kthreads before destroying vCPUs, as + * iterating over vCPUs in a different task while vCPUs are being freed + * is unsafe, i.e. will lead to use-after-free. The PIT also needs to + * be stopped before IRQ routing is freed. + */ + cancel_delayed_work_sync(&kvm->arch.kvmclock_sync_work); + cancel_delayed_work_sync(&kvm->arch.kvmclock_update_work); + + kvm_free_pit(kvm); + kvm_mmu_pre_destroy_vm(kvm); } -- 2.48.1.658.g4767266eb4-goog