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AJvYcCVynInSvFBMmRZRVTxdYBI3jIKNTFh1AZ5kxkLJFblZ/U6+6yicFRNpaywnLkpsfI0asYRZ2ugOuS9b6jk=@vger.kernel.org X-Gm-Message-State: AOJu0Yz08TCOVf3dXlnYgkX4d7K5zpvL7Kcv7Tlgm4uNPwW+LKHfLjdS 23khXQ54KeGtBWO7BMsUHlv0EJblJxvhhp4O91B+JjuAKQaT1G3ojNwCXBcly/JTnxWz8V9tvRu Xsg== X-Google-Smtp-Source: AGHT+IEwiOscwRryNbV5HEkDLR/QSN5uMa5G6pQrJMGE0vv7idD4Yujycc133PfZgsKp3+f0KyatWMvuqqA= X-Received: from pjwx11.prod.google.com ([2002:a17:90a:c2cb:b0:2ea:29de:af10]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ef11:b0:224:2384:5b40 with SMTP id d9443c01a7336-22c535a7e46mr72675585ad.24.1745025143192; Fri, 18 Apr 2025 18:12:23 -0700 (PDT) Date: Fri, 18 Apr 2025 18:12:21 -0700 In-Reply-To: <20250417131945.109053-2-adrian.hunter@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250417131945.109053-1-adrian.hunter@intel.com> <20250417131945.109053-2-adrian.hunter@intel.com> Message-ID: Subject: Re: [PATCH V2 1/1] KVM: TDX: Add sub-ioctl KVM_TDX_TERMINATE_VM From: Sean Christopherson To: Adrian Hunter Cc: pbonzini@redhat.com, mlevitsk@redhat.com, kvm@vger.kernel.org, rick.p.edgecombe@intel.com, kirill.shutemov@linux.intel.com, kai.huang@intel.com, reinette.chatre@intel.com, xiaoyao.li@intel.com, tony.lindgren@linux.intel.com, binbin.wu@linux.intel.com, isaku.yamahata@intel.com, linux-kernel@vger.kernel.org, yan.y.zhao@intel.com, chao.gao@intel.com Content-Type: text/plain; charset="us-ascii" On Thu, Apr 17, 2025, Adrian Hunter wrote: > From: Sean Christopherson > > Add sub-ioctl KVM_TDX_TERMINATE_VM to release the HKID prior to shutdown, > which enables more efficient reclaim of private memory. > > Private memory is removed from MMU/TDP when guest_memfds are closed. If > the HKID has not been released, the TDX VM is still in RUNNABLE state, > so pages must be removed using "Dynamic Page Removal" procedure (refer > TDX Module Base spec) which involves a number of steps: > Block further address translation > Exit each VCPU > Clear Secure EPT entry > Flush/write-back/invalidate relevant caches > > However, when the HKID is released, the TDX VM moves to TD_TEARDOWN state > where all TDX VM pages are effectively unmapped, so pages can be reclaimed > directly. > > Reclaiming TD Pages in TD_TEARDOWN State was seen to decrease the total > reclaim time. For example: > > VCPUs Size (GB) Before (secs) After (secs) > 4 18 72 24 > 32 107 517 134 > 64 400 5539 467 > > [Adrian: wrote commit message, added KVM_TDX_TERMINATE_VM documentation, > and moved cpus_read_lock() inside kvm->lock for consistency as reported > by lockdep] /facepalm I over-thought this. We've had an long-standing battle with kvm_lock vs. cpus_read_lock(), but this is kvm->lock, not kvm_lock. /sigh > +static int tdx_terminate_vm(struct kvm *kvm) > +{ > + int r = 0; > + > + guard(mutex)(&kvm->lock); With kvm->lock taken outside cpus_read_lock(), just handle KVM_TDX_TERMINATE_VM in the switch statement, i.e. let tdx_vm_ioctl() deal with kvm->lock. > + cpus_read_lock(); > + > + if (!kvm_trylock_all_vcpus(kvm)) { > + r = -EBUSY; > + goto out; > + } > + > + kvm_vm_dead(kvm); > + kvm_unlock_all_vcpus(kvm); > + > + __tdx_release_hkid(kvm, true); > +out: > + cpus_read_unlock(); > + return r; > +} > + > int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) > { > struct kvm_tdx_cmd tdx_cmd; > @@ -2805,6 +2827,9 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) > if (tdx_cmd.hw_error) > return -EINVAL; > > + if (tdx_cmd.id == KVM_TDX_TERMINATE_VM) > + return tdx_terminate_vm(kvm); > + > mutex_lock(&kvm->lock); > > switch (tdx_cmd.id) { > -- > 2.43.0 >