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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id l29-20020a63ba5d000000b00438834b14a1sm6064695pgu.80.2022.11.14.08.32.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Nov 2022 08:32:37 -0800 (PST) Date: Mon, 14 Nov 2022 16:32:34 +0000 From: Sean Christopherson To: Yan Zhao Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, intel-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, zhenyuw@linux.intel.com Subject: Re: [PATCH v2 1/3] KVM: x86: add a new page track hook track_remove_slot Message-ID: References: <20221111103247.22275-1-yan.y.zhao@intel.com> <20221111103350.22326-1-yan.y.zhao@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Nov 14, 2022, Yan Zhao wrote: > On Sat, Nov 12, 2022 at 12:43:07AM +0000, Sean Christopherson wrote: > > On Sat, Nov 12, 2022, Yan Zhao wrote: > > > And I'm also not sure if a slots_arch_lock is required for > > > kvm_slot_page_track_add_page() and kvm_slot_page_track_remove_page(). > > > > It's not required. slots_arch_lock protects interaction between memslot updates > In kvm_slot_page_track_add_page() and kvm_slot_page_track_remove_page(), > slot->arch.gfn_track[mode][index] is updated in update_gfn_track(), > do you know which lock is used to protect it? mmu_lock protects the count, kvm->srcu protects the slot, and shadow_root_allocated protects that validity of gfn_track, i.e. shadow_root_allocated ensures that KVM allocates gfn_track for all memslots when shadow paging is activated. The cleanup series I'm prepping adds lockdep assertions for the relevant paths, e.g. $ git grep -B 8 -E "update_gfn_write_track.*;" arch/x86/kvm/mmu/page_track.c-void __kvm_write_track_add_gfn(struct kvm *kvm, struct kvm_memory_slot *slot, arch/x86/kvm/mmu/page_track.c- gfn_t gfn) arch/x86/kvm/mmu/page_track.c-{ arch/x86/kvm/mmu/page_track.c- lockdep_assert_held_write(&kvm->mmu_lock); arch/x86/kvm/mmu/page_track.c- arch/x86/kvm/mmu/page_track.c- if (KVM_BUG_ON(!kvm_page_track_write_tracking_enabled(kvm), kvm)) arch/x86/kvm/mmu/page_track.c- return; arch/x86/kvm/mmu/page_track.c- arch/x86/kvm/mmu/page_track.c: update_gfn_write_track(slot, gfn, 1); -- arch/x86/kvm/mmu/page_track.c-void __kvm_write_track_remove_gfn(struct kvm *kvm, arch/x86/kvm/mmu/page_track.c- struct kvm_memory_slot *slot, gfn_t gfn) arch/x86/kvm/mmu/page_track.c-{ arch/x86/kvm/mmu/page_track.c- lockdep_assert_held_write(&kvm->mmu_lock); arch/x86/kvm/mmu/page_track.c- arch/x86/kvm/mmu/page_track.c- if (KVM_BUG_ON(!kvm_page_track_write_tracking_enabled(kvm), kvm)) arch/x86/kvm/mmu/page_track.c- return; arch/x86/kvm/mmu/page_track.c- arch/x86/kvm/mmu/page_track.c: update_gfn_write_track(slot, gfn, -1);