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Tue, 25 Feb 2025 07:04:56 -0800 (PST) Date: Tue, 25 Feb 2025 07:04:55 -0800 In-Reply-To: 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> <20250224235542.2562848-2-seanjc@google.com> Message-ID: Subject: Re: [PATCH 1/7] KVM: x86: Free vCPUs before freeing VM state From: Sean Christopherson To: Yan Zhao Cc: 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 , Paolo Bonzini , 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 , Rick P Edgecombe , Kai Huang , Isaku Yamahata Content-Type: text/plain; charset="us-ascii" On Tue, Feb 25, 2025, Yan Zhao wrote: > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 58b82d6fd77c..045c61cc7e54 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -12890,11 +12890,11 @@ void kvm_arch_destroy_vm(struct kvm *kvm) > > mutex_unlock(&kvm->slots_lock); > > } > > kvm_unload_vcpu_mmus(kvm); > > + kvm_destroy_vcpus(kvm); > > kvm_x86_call(vm_destroy)(kvm); > > kvm_free_msr_filter(srcu_dereference_check(kvm->arch.msr_filter, &kvm->srcu, 1)); > > kvm_pic_destroy(kvm); > > kvm_ioapic_destroy(kvm); > > - kvm_destroy_vcpus(kvm); > > kvfree(rcu_dereference_check(kvm->arch.apic_map, 1)); > > kfree(srcu_dereference_check(kvm->arch.pmu_event_filter, &kvm->srcu, 1)); > > kvm_mmu_uninit_vm(kvm); > After this change, now the sequence is that > > 1. kvm_arch_pre_destroy_vm() > 2. kvm_arch_destroy_vm() > 2.1 kvm_destroy_vcpus() > 2.2 .vm_destroy hook > 2.3 kvm_mmu_uninit_vm() --> mirror root ref is 1 upon here. Zap the mirror > root and reclaim SETP page table pages. > 2.4 .vm_free hook > > Since TDX needs to reclaim the TDR page after reclaiming all other pages, we > currently added a vm_free hook at 2.4, after 2.3. > > Could we move kvm_mmu_uninit_vm() before the .vm_destroy hook and after > kvm_destroy_vcpus()? > > Or move the .vm_destroy hook after kvm_mmu_uninit_vm(), e.g. after > kvm_page_track_cleanup()? I would go for the first option. I'll tack on a patch since I need to test all of these flows anyways, and I would much prefer to change course sooner rather than later if it doesn't work for whatever reason. Is this comment accurate? diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1e5f6f820c0b..f5685f153e08 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12874,13 +12874,19 @@ void kvm_arch_destroy_vm(struct kvm *kvm) mutex_unlock(&kvm->slots_lock); } kvm_destroy_vcpus(kvm); + + /* + * Do final MMU teardown prior to calling into vendor code. All pages + * that were donated to the TDX module, e.g. for S-EPT tables, need to + * be reclaimed before the VM metadata page can be freed. + */ + kvm_mmu_uninit_vm(kvm); kvm_x86_call(vm_destroy)(kvm); kvm_free_msr_filter(srcu_dereference_check(kvm->arch.msr_filter, &kvm->srcu, 1)); kvm_pic_destroy(kvm); kvm_ioapic_destroy(kvm); kvfree(rcu_dereference_check(kvm->arch.apic_map, 1)); kfree(srcu_dereference_check(kvm->arch.pmu_event_filter, &kvm->srcu, 1)); - kvm_mmu_uninit_vm(kvm); kvm_page_track_cleanup(kvm); kvm_xen_destroy_vm(kvm); kvm_hv_destroy_vm(kvm);