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Fri, 26 May 2023 16:44:49 -0700 (PDT) Date: Fri, 26 May 2023 17:44:31 -0600 In-Reply-To: <20230526234435.662652-1-yuzhao@google.com> Message-Id: <20230526234435.662652-7-yuzhao@google.com> Mime-Version: 1.0 References: <20230526234435.662652-1-yuzhao@google.com> X-Mailer: git-send-email 2.41.0.rc0.172.g3f132b7071-goog Subject: [PATCH mm-unstable v2 06/10] kvm/powerpc: make radix page tables RCU safe From: Yu Zhao To: Andrew Morton , Paolo Bonzini X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Jason A. Donenfeld" , x86@kernel.org, Gavin Shan , kvm@vger.kernel.org, linux-doc@vger.kernel.org, Catalin Marinas , Dave Hansen , Peter Xu , linux-mm@kvack.org, Ben Gardon , Chao Peng , Will Deacon , Gaosheng Cui , Marc Zyngier , "H. Peter Anvin" , Yu Zhao , Jonathan Corbet , Alistair Popple , Jason Gunthorpe , Ingo Molnar , Zenghui Yu , linux-trace-kernel@vger.kernel.org, linux-mm@google.com, Thomas Huth , Suzuki K Poulose , Nicholas Piggin , Borislav Petkov , Steven Rostedt , kvmarm@lists.linux.dev, Thomas Gleixner , linux-arm-ke rnel@lists.infradead.org, Fabiano Rosas , Michael Larabel , Sean Christopherson , linux-kernel@vger.kernel.org, Oliver Upton , James Morse , Masami Hiramatsu , Anup Patel , linuxppc-dev@lists.ozlabs.org, Mike Rapoport Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" KVM page tables are currently not RCU safe against remapping, i.e., kvmppc_unmap_free_pmd_entry_table() et al. The previous mmu_notifier_ops members rely on kvm->mmu_lock to synchronize with that operation. However, the new mmu_notifier_ops member test_clear_young() provides a fast path that does not take kvm->mmu_lock. To implement kvm_arch_test_clear_young() for that path, orphan page tables need to be freed by RCU. Unmapping, specifically kvm_unmap_radix(), does not free page tables, hence not a concern. Signed-off-by: Yu Zhao --- arch/powerpc/kvm/book3s_64_mmu_radix.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index 461307b89c3a..3b65b3b11041 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -1469,13 +1469,15 @@ int kvmppc_radix_init(void) { unsigned long size = sizeof(void *) << RADIX_PTE_INDEX_SIZE; - kvm_pte_cache = kmem_cache_create("kvm-pte", size, size, 0, pte_ctor); + kvm_pte_cache = kmem_cache_create("kvm-pte", size, size, + SLAB_TYPESAFE_BY_RCU, pte_ctor); if (!kvm_pte_cache) return -ENOMEM; size = sizeof(void *) << RADIX_PMD_INDEX_SIZE; - kvm_pmd_cache = kmem_cache_create("kvm-pmd", size, size, 0, pmd_ctor); + kvm_pmd_cache = kmem_cache_create("kvm-pmd", size, size, + SLAB_TYPESAFE_BY_RCU, pmd_ctor); if (!kvm_pmd_cache) { kmem_cache_destroy(kvm_pte_cache); return -ENOMEM;