From fcc5bf89635a05e627cdd2e9ec52c989c8dfe2ab Mon Sep 17 00:00:00 2001 From: Jing Zhang Date: Tue, 18 Jan 2022 01:57:01 +0000 Subject: [PATCH 1/3] KVM: arm64: Use read/write spin lock for MMU protection Replace MMU spinlock with rwlock and update all instances of the lock being acquired with a write lock acquisition. Future commit will add a fast path for permission relaxation during dirty logging under a read lock. Signed-off-by: Jing Zhang Tested-by: Fuad Tabba Reviewed-by: Fuad Tabba Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20220118015703.3630552-2-jingzhangos@google.com --- arch/arm64/include/asm/kvm_host.h | 2 ++ arch/arm64/kvm/mmu.c | 36 +++++++++++++++---------------- 2 files changed, 20 insertions(+), 18 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 5bc01e62c08a..4866842c31e1 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -50,6 +50,8 @@ #define KVM_DIRTY_LOG_MANUAL_CAPS (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \ KVM_DIRTY_LOG_INITIALLY_SET) +#define KVM_HAVE_MMU_RWLOCK + /* * Mode of operation configurable with kvm-arm.mode early param. * See Documentation/admin-guide/kernel-parameters.txt for more information. diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index bc2aba953299..cafd5813c949 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -58,7 +58,7 @@ static int stage2_apply_range(struct kvm *kvm, phys_addr_t addr, break; if (resched && next != end) - cond_resched_lock(&kvm->mmu_lock); + cond_resched_rwlock_write(&kvm->mmu_lock); } while (addr = next, addr != end); return ret; @@ -179,7 +179,7 @@ static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu); phys_addr_t end = start + size; - assert_spin_locked(&kvm->mmu_lock); + lockdep_assert_held_write(&kvm->mmu_lock); WARN_ON(size & ~PAGE_MASK); WARN_ON(stage2_apply_range(kvm, start, end, kvm_pgtable_stage2_unmap, may_block)); @@ -213,13 +213,13 @@ static void stage2_flush_vm(struct kvm *kvm) int idx, bkt; idx = srcu_read_lock(&kvm->srcu); - spin_lock(&kvm->mmu_lock); + write_lock(&kvm->mmu_lock); slots = kvm_memslots(kvm); kvm_for_each_memslot(memslot, bkt, slots) stage2_flush_memslot(kvm, memslot); - spin_unlock(&kvm->mmu_lock); + write_unlock(&kvm->mmu_lock); srcu_read_unlock(&kvm->srcu, idx); } @@ -720,13 +720,13 @@ void stage2_unmap_vm(struct kvm *kvm) idx = srcu_read_lock(&kvm->srcu); mmap_read_lock(current->mm); - spin_lock(&kvm->mmu_lock); + write_lock(&kvm->mmu_lock); slots = kvm_memslots(kvm); kvm_for_each_memslot(memslot, bkt, slots) stage2_unmap_memslot(kvm, memslot); - spin_unlock(&kvm->mmu_lock); + write_unlock(&kvm->mmu_lock); mmap_read_unlock(current->mm); srcu_read_unlock(&kvm->srcu, idx); } @@ -736,14 +736,14 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu); struct kvm_pgtable *pgt = NULL; - spin_lock(&kvm->mmu_lock); + write_lock(&kvm->mmu_lock); pgt = mmu->pgt; if (pgt) { mmu->pgd_phys = 0; mmu->pgt = NULL; free_percpu(mmu->last_vcpu_ran); } - spin_unlock(&kvm->mmu_lock); + write_unlock(&kvm->mmu_lock); if (pgt) { kvm_pgtable_stage2_destroy(pgt); @@ -783,10 +783,10 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa, if (ret) break; - spin_lock(&kvm->mmu_lock); + write_lock(&kvm->mmu_lock); ret = kvm_pgtable_stage2_map(pgt, addr, PAGE_SIZE, pa, prot, &cache); - spin_unlock(&kvm->mmu_lock); + write_unlock(&kvm->mmu_lock); if (ret) break; @@ -834,9 +834,9 @@ static void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot) start = memslot->base_gfn << PAGE_SHIFT; end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT; - spin_lock(&kvm->mmu_lock); + write_lock(&kvm->mmu_lock); stage2_wp_range(&kvm->arch.mmu, start, end); - spin_unlock(&kvm->mmu_lock); + write_unlock(&kvm->mmu_lock); kvm_flush_remote_tlbs(kvm); } @@ -1212,7 +1212,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, if (exec_fault && device) return -ENOEXEC; - spin_lock(&kvm->mmu_lock); + write_lock(&kvm->mmu_lock); pgt = vcpu->arch.hw_mmu->pgt; if (mmu_notifier_retry(kvm, mmu_seq)) goto out_unlock; @@ -1271,7 +1271,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, } out_unlock: - spin_unlock(&kvm->mmu_lock); + write_unlock(&kvm->mmu_lock); kvm_set_pfn_accessed(pfn); kvm_release_pfn_clean(pfn); return ret != -EAGAIN ? ret : 0; @@ -1286,10 +1286,10 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa) trace_kvm_access_fault(fault_ipa); - spin_lock(&vcpu->kvm->mmu_lock); + write_lock(&vcpu->kvm->mmu_lock); mmu = vcpu->arch.hw_mmu; kpte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa); - spin_unlock(&vcpu->kvm->mmu_lock); + write_unlock(&vcpu->kvm->mmu_lock); pte = __pte(kpte); if (pte_valid(pte)) @@ -1692,9 +1692,9 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm, gpa_t gpa = slot->base_gfn << PAGE_SHIFT; phys_addr_t size = slot->npages << PAGE_SHIFT; - spin_lock(&kvm->mmu_lock); + write_lock(&kvm->mmu_lock); unmap_stage2_range(&kvm->arch.mmu, gpa, size); - spin_unlock(&kvm->mmu_lock); + write_unlock(&kvm->mmu_lock); } /* From f783ef1c0e82e4fc311a972472ff61f6d1d0e22d Mon Sep 17 00:00:00 2001 From: Jing Zhang Date: Tue, 18 Jan 2022 01:57:02 +0000 Subject: [PATCH 2/3] KVM: arm64: Add fast path to handle permission relaxation during dirty logging To reduce MMU lock contention during dirty logging, all permission relaxation operations would be performed under read lock. Signed-off-by: Jing Zhang Tested-by: Fuad Tabba Reviewed-by: Fuad Tabba Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20220118015703.3630552-3-jingzhangos@google.com --- arch/arm64/kvm/mmu.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index cafd5813c949..10df5d855d54 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1080,6 +1080,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, gfn_t gfn; kvm_pfn_t pfn; bool logging_active = memslot_is_logging(memslot); + bool logging_perm_fault = false; unsigned long fault_level = kvm_vcpu_trap_get_fault_level(vcpu); unsigned long vma_pagesize, fault_granule; enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R; @@ -1114,6 +1115,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, if (logging_active) { force_pte = true; vma_shift = PAGE_SHIFT; + logging_perm_fault = (fault_status == FSC_PERM && write_fault); } else { vma_shift = get_vma_page_shift(vma, hva); } @@ -1212,7 +1214,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, if (exec_fault && device) return -ENOEXEC; - write_lock(&kvm->mmu_lock); + /* + * To reduce MMU contentions and enhance concurrency during dirty + * logging dirty logging, only acquire read lock for permission + * relaxation. + */ + if (logging_perm_fault) + read_lock(&kvm->mmu_lock); + else + write_lock(&kvm->mmu_lock); pgt = vcpu->arch.hw_mmu->pgt; if (mmu_notifier_retry(kvm, mmu_seq)) goto out_unlock; @@ -1271,7 +1281,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, } out_unlock: - write_unlock(&kvm->mmu_lock); + if (logging_perm_fault) + read_unlock(&kvm->mmu_lock); + else + write_unlock(&kvm->mmu_lock); kvm_set_pfn_accessed(pfn); kvm_release_pfn_clean(pfn); return ret != -EAGAIN ? ret : 0; From c340f7899af6f83bd937f8838949bb32da54c8a4 Mon Sep 17 00:00:00 2001 From: Jing Zhang Date: Tue, 18 Jan 2022 01:57:03 +0000 Subject: [PATCH 3/3] KVM: selftests: Add vgic initialization for dirty log perf test for ARM For ARM64, if no vgic is setup before the dirty log perf test, the userspace irqchip would be used, which would affect the dirty log perf test result. Signed-off-by: Jing Zhang Tested-by: Fuad Tabba Reviewed-by: Fuad Tabba Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20220118015703.3630552-4-jingzhangos@google.com --- tools/testing/selftests/kvm/dirty_log_perf_test.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c index 1954b964d1cf..b501338d9430 100644 --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c @@ -18,6 +18,12 @@ #include "test_util.h" #include "perf_test_util.h" #include "guest_modes.h" +#ifdef __aarch64__ +#include "aarch64/vgic.h" + +#define GICD_BASE_GPA 0x8000000ULL +#define GICR_BASE_GPA 0x80A0000ULL +#endif /* How many host loops to run by default (one KVM_GET_DIRTY_LOG for each loop)*/ #define TEST_HOST_LOOP_N 2UL @@ -200,6 +206,10 @@ static void run_test(enum vm_guest_mode mode, void *arg) vm_enable_cap(vm, &cap); } +#ifdef __aarch64__ + vgic_v3_setup(vm, nr_vcpus, 64, GICD_BASE_GPA, GICR_BASE_GPA); +#endif + /* Start the iterations */ iteration = 0; host_quit = false;