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 <jingzhangos@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220118015703.3630552-2-jingzhangos@google.com

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 5bc01e6..4866842 100644 (file)
--- 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 bc2aba9..cafd581 100644 (file)
--- 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);
 }
 
 /*