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Fri, 09 Feb 2024 14:29:00 -0800 (PST) Reply-To: Sean Christopherson Date: Fri, 9 Feb 2024 14:28:54 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240209222858.396696-1-seanjc@google.com> Subject: [PATCH v4 0/4] KVM: x86/mmu: Pre-check for mmu_notifier retry From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yan Zhao , Friedrich Weber , Kai Huang , Yuan Yao , Xu Yilun , Yu Zhang , Chao Peng , Fuad Tabba , Michael Roth , Isaku Yamahata , David Matlack X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790462158757946527 X-GMAIL-MSGID: 1790462158757946527 Retry page faults without acquiring mmu_lock, and potentially even without resolving a pfn, if the gfn is covered by an active invalidation. This avoids resource and lock contention, which can be especially beneficial for preemptible kernels as KVM can get stuck bouncing mmu_lock between a vCPU and the invalidation task the vCPU is waiting on to finish. v4: - Pre-check for retry before resolving the pfn, too. [Yan] - Add a patch to fix a private/shared vs. memslot validity check priority inversion bug. - Refactor kvm_faultin_pfn() to clean up the handling of noslot faults. v3: - https://lkml.kernel.org/r/20240203003518.387220-1-seanjc%40google.com - Release the pfn, i.e. put the struct page reference if one was held, as the caller doesn't expect to get a reference on "failure". [Yuan] - Fix a typo in the comment. v2: - Introduce a dedicated helper and collapse to a single patch (because adding an unused helper would be quite silly). - Add a comment to explain the "unsafe" check in kvm_faultin_pfn(). [Kai] - Add Kai's Ack. v1: https://lore.kernel.org/all/20230825020733.2849862-1-seanjc@google.com Sean Christopherson (4): KVM: x86/mmu: Retry fault before acquiring mmu_lock if mapping is changing KVM: x86/mmu: Move private vs. shared check above slot validity checks KVM: x86/mmu: Move slot checks from __kvm_faultin_pfn() to kvm_faultin_pfn() KVM: x86/mmu: Handle no-slot faults at the beginning of kvm_faultin_pfn() arch/x86/kvm/mmu/mmu.c | 134 ++++++++++++++++++++++---------- arch/x86/kvm/mmu/mmu_internal.h | 5 +- include/linux/kvm_host.h | 26 +++++++ 3 files changed, 122 insertions(+), 43 deletions(-) base-commit: 60eedcfceda9db46f1b333e5e1aa9359793f04fb