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Fri, 26 May 2023 16:44:50 -0700 (PDT) Date: Fri, 26 May 2023 17:44:32 -0600 In-Reply-To: <20230526234435.662652-1-yuzhao@google.com> Message-Id: <20230526234435.662652-8-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 07/10] kvm/powerpc: add kvm_arch_test_clear_young() 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" Implement kvm_arch_test_clear_young() to support the fast path in mmu_notifier_ops->test_clear_young(). It focuses on a simple case, i.e., radix MMU sets the accessed bit in KVM PTEs and VMs are not nested, where it can rely on RCU and pte_xchg() to safely clear the accessed bit without taking kvm->mmu_lock. Complex cases fall back to the existing slow path where kvm->mmu_lock is then taken. Signed-off-by: Yu Zhao --- arch/powerpc/include/asm/kvm_host.h | 8 ++++ arch/powerpc/include/asm/kvm_ppc.h | 1 + arch/powerpc/kvm/book3s.c | 6 +++ arch/powerpc/kvm/book3s.h | 1 + arch/powerpc/kvm/book3s_64_mmu_radix.c | 59 ++++++++++++++++++++++++++ arch/powerpc/kvm/book3s_hv.c | 5 +++ 6 files changed, 80 insertions(+) diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 14ee0dece853..75c260ea8a9e 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -883,4 +883,12 @@ static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {} static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {} static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {} +#define kvm_arch_has_test_clear_young kvm_arch_has_test_clear_young +static inline bool kvm_arch_has_test_clear_young(void) +{ + return IS_ENABLED(CONFIG_KVM_BOOK3S_HV_POSSIBLE) && + cpu_has_feature(CPU_FTR_HVMODE) && cpu_has_feature(CPU_FTR_ARCH_300) && + radix_enabled(); +} + #endif /* __POWERPC_KVM_HOST_H__ */ diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h index 79a9c0bb8bba..ff1af6a7b44f 100644 --- a/arch/powerpc/include/asm/kvm_ppc.h +++ b/arch/powerpc/include/asm/kvm_ppc.h @@ -287,6 +287,7 @@ struct kvmppc_ops { bool (*unmap_gfn_range)(struct kvm *kvm, struct kvm_gfn_range *range); bool (*age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range); bool (*test_age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range); + bool (*test_clear_young)(struct kvm *kvm, struct kvm_gfn_range *range); bool (*set_spte_gfn)(struct kvm *kvm, struct kvm_gfn_range *range); void (*free_memslot)(struct kvm_memory_slot *slot); int (*init_vm)(struct kvm *kvm); diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c index 686d8d9eda3e..37bf40b0c4ff 100644 --- a/arch/powerpc/kvm/book3s.c +++ b/arch/powerpc/kvm/book3s.c @@ -899,6 +899,12 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) return kvm->arch.kvm_ops->test_age_gfn(kvm, range); } +bool kvm_arch_test_clear_young(struct kvm *kvm, struct kvm_gfn_range *range) +{ + return !kvm->arch.kvm_ops->test_clear_young || + kvm->arch.kvm_ops->test_clear_young(kvm, range); +} + bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { return kvm->arch.kvm_ops->set_spte_gfn(kvm, range); diff --git a/arch/powerpc/kvm/book3s.h b/arch/powerpc/kvm/book3s.h index 58391b4b32ed..fa2659e21ccc 100644 --- a/arch/powerpc/kvm/book3s.h +++ b/arch/powerpc/kvm/book3s.h @@ -12,6 +12,7 @@ extern void kvmppc_core_flush_memslot_hv(struct kvm *kvm, extern bool kvm_unmap_gfn_range_hv(struct kvm *kvm, struct kvm_gfn_range *range); extern bool kvm_age_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range); extern bool kvm_test_age_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range); +extern bool kvm_test_clear_young_hv(struct kvm *kvm, struct kvm_gfn_range *range); extern bool kvm_set_spte_gfn_hv(struct kvm *kvm, struct kvm_gfn_range *range); extern int kvmppc_mmu_init_pr(struct kvm_vcpu *vcpu); diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index 3b65b3b11041..0a392e9a100a 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -1088,6 +1088,65 @@ bool kvm_test_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot, return ref; } +bool kvm_test_clear_young_hv(struct kvm *kvm, struct kvm_gfn_range *range) +{ + bool err; + gfn_t gfn = range->start; + + rcu_read_lock(); + + err = !kvm_is_radix(kvm); + if (err) + goto unlock; + + /* + * Case 1: This function kvmppc_switch_mmu_to_hpt() + * + * rcu_read_lock() + * Test kvm_is_radix() kvm->arch.radix = 0 + * Use kvm->arch.pgtable synchronize_rcu() + * rcu_read_unlock() + * kvmppc_free_radix() + * + * + * Case 2: This function kvmppc_switch_mmu_to_radix() + * + * kvmppc_init_vm_radix() + * smp_wmb() + * Test kvm_is_radix() kvm->arch.radix = 1 + * smp_rmb() + * Use kvm->arch.pgtable + */ + smp_rmb(); + + while (gfn < range->end) { + pte_t *ptep; + pte_t old, new; + unsigned int shift; + + ptep = find_kvm_secondary_pte_unlocked(kvm, gfn * PAGE_SIZE, &shift); + if (!ptep) + goto next; + + VM_WARN_ON_ONCE(!page_count(virt_to_page(ptep))); + + old = READ_ONCE(*ptep); + if (!pte_present(old) || !pte_young(old)) + goto next; + + new = pte_mkold(old); + + if (kvm_should_clear_young(range, gfn)) + pte_xchg(ptep, old, new); +next: + gfn += shift ? BIT(shift - PAGE_SHIFT) : 1; + } +unlock: + rcu_read_unlock(); + + return err; +} + /* Returns the number of PAGE_SIZE pages that are dirty */ static int kvm_radix_test_clear_dirty(struct kvm *kvm, struct kvm_memory_slot *memslot, int pagenum) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 130bafdb1430..20a81ec9fde8 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -5262,6 +5262,8 @@ int kvmppc_switch_mmu_to_hpt(struct kvm *kvm) spin_lock(&kvm->mmu_lock); kvm->arch.radix = 0; spin_unlock(&kvm->mmu_lock); + /* see the comments in kvm_test_clear_young_hv() */ + synchronize_rcu(); kvmppc_free_radix(kvm); lpcr = LPCR_VPM1; @@ -5286,6 +5288,8 @@ int kvmppc_switch_mmu_to_radix(struct kvm *kvm) if (err) return err; kvmppc_rmap_reset(kvm); + /* see the comments in kvm_test_clear_young_hv() */ + smp_wmb(); /* Mutual exclusion with kvm_unmap_gfn_range etc. */ spin_lock(&kvm->mmu_lock); kvm->arch.radix = 1; @@ -6185,6 +6189,7 @@ static struct kvmppc_ops kvm_ops_hv = { .unmap_gfn_range = kvm_unmap_gfn_range_hv, .age_gfn = kvm_age_gfn_hv, .test_age_gfn = kvm_test_age_gfn_hv, + .test_clear_young = kvm_test_clear_young_hv, .set_spte_gfn = kvm_set_spte_gfn_hv, .free_memslot = kvmppc_core_free_memslot_hv, .init_vm = kvmppc_core_init_vm_hv,