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[34.125.73.210]) by smtp.gmail.com with ESMTPSA id lr31-20020a056a00739f00b006ecfe1c9630sm3368108pfb.92.2024.04.12.13.44.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Apr 2024 13:44:45 -0700 (PDT) Date: Fri, 12 Apr 2024 13:44:41 -0700 From: David Matlack To: James Houghton Cc: Andrew Morton , Paolo Bonzini , Yu Zhao , Marc Zyngier , Oliver Upton , Sean Christopherson , Jonathan Corbet , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Shaoqin Huang , Gavin Shan , Ricardo Koller , Raghavendra Rao Ananta , Ryan Roberts , David Rientjes , Axel Rasmussen , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3 5/7] KVM: x86: Participate in bitmap-based PTE aging Message-ID: References: <20240401232946.1837665-1-jthoughton@google.com> <20240401232946.1837665-6-jthoughton@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240401232946.1837665-6-jthoughton@google.com> X-Rspam-User: X-Stat-Signature: bu3iyp7pyf6kz6rz1w3y3bgp9fs195bz X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 29744100003 X-HE-Tag: 1712954686-793803 X-HE-Meta: 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 61Z56S+l cvVWJmk76LU6cduYjOu8IK8yFEzWKg+ACMdNMizr+89FifjrFJ6ik8NpJ66717xoM6qw2QetTxyhmb7kfkyx7HkRmRtc0YiQxUURrRvPIMBs7xd81NeRC3ZXETouecd8XOYr6cmw1zcxfRxDXGiHN6YT2GdTn1TOzrHAucLYoSu6rxzFO4+6zmRixAumqmtiyeGxwStZLr1swyqhp7Cw7oJ6jx2zfAR1vavh+qKjuOBHe3bTbI9ffOtjFPMLwnpMlOO/O3sMtq3GJTO6TYo68xgs7h8O95Hs92xqdgpwwVChRN6Yu+dcg0nnF3mlO+3Z2qElYih8qs34/tlNQaVlTBwbmwk5aSosMCzrXe79HS6q9nsT7QVwXI7q1Qsdfq8o0DPB2da2l8DMhXzWPRLjq5IB2S5102FOO8E54BnfiI8X8vxw4v4b/5ymbVYHPbGcS15zJK0vPPuFnSZ/cO71sglJqNQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000063, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024-04-01 11:29 PM, James Houghton wrote: > Only handle the TDP MMU case for now. In other cases, if a bitmap was > not provided, fallback to the slowpath that takes mmu_lock, or, if a > bitmap was provided, inform the caller that the bitmap is unreliable. I think this patch will trigger a lockdep assert in kvm_tdp_mmu_age_gfn_range kvm_tdp_mmu_handle_gfn for_each_tdp_mmu_root __for_each_tdp_mmu_root kvm_lockdep_assert_mmu_lock_held ... because it walks tdp_mmu_roots without holding mmu_lock. Yu's patch[1] added a lockless walk to the TDP MMU. We'd need something similar here and also update the comment above tdp_mmu_roots describing how tdp_mmu_roots can be read locklessly. [1] https://lore.kernel.org/kvmarm/ZItX64Bbx5vdjo9M@google.com/