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Mon, 04 May 2026 15:42:48 -0700 (PDT) Date: Mon, 4 May 2026 22:42:11 +0000 In-Reply-To: <20260504224213.1049426-1-jthoughton@google.com> Mime-Version: 1.0 References: <20260504224213.1049426-1-jthoughton@google.com> X-Mailer: git-send-email 2.54.0.545.g6539524ca2-goog Message-ID: <20260504224213.1049426-5-jthoughton@google.com> Subject: [PATCH 4/5] KVM: Hold MMU lock exclusively when calling kvm_arch_flush_shadow_all() From: James Houghton To: Paolo Bonzini Cc: Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Sean Christopherson , Gavin Shan , Shaoqin Huang , Ricardo Koller , Tianrui Zhao , Bibo Mao , Huacai Chen , James Hogan , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, James Houghton Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260504_154250_356035_9FCD154F X-CRM114-Status: GOOD ( 17.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org All architectures that non-trivially implement this function grab the KVM MMU lock exclusively to prevent things like double-freeing of page table entries and caches. Do so generically to somewhat simplify the architecture-specific logic. Without this change, it is possible for kvm_arch_flush_shadow_all() to be called on the same `kvm` at the same time: if the `kvm`'s mm is destroyed (exit_mm()) at the same time to the final reference to the `kvm` is dropped. Signed-off-by: James Houghton --- arch/arm64/kvm/nested.c | 2 +- arch/loongarch/kvm/mmu.c | 4 +++- arch/mips/kvm/mips.c | 2 +- arch/riscv/kvm/mmu.c | 4 ++-- arch/riscv/kvm/vm.c | 2 ++ arch/x86/kvm/mmu/mmu.c | 4 +--- virt/kvm/kvm_main.c | 3 +++ 7 files changed, 13 insertions(+), 8 deletions(-) diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 977598bff5e6..ba2e6c98bd45 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1190,7 +1190,7 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm) { int i; - guard(write_lock)(&kvm->mmu_lock); + lockdep_assert_held_write(&kvm->mmu_lock); for (i = 0; i < kvm->arch.nested_mmus_size; i++) { struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c index 5dbce9b18e1c..120001da26e4 100644 --- a/arch/loongarch/kvm/mmu.c +++ b/arch/loongarch/kvm/mmu.c @@ -486,7 +486,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, void kvm_arch_flush_shadow_all(struct kvm *kvm) { - kvm_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT, 1); + lockdep_assert_held(&kvm->mmu_lock); + + kvm_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT, 0); } void kvm_arch_flush_shadow_memslot(struct kvm *kvm, struct kvm_memory_slot *slot) diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 463b6c4aa62c..4ad9e21a3321 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -180,7 +180,7 @@ long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl, void kvm_arch_flush_shadow_all(struct kvm *kvm) { - guard(spinlock)(&kvm->mmu_lock); + lockdep_assert_held(&kvm->mmu_lock); /* Flush whole GPA */ kvm_mips_flush_gpa_pt(kvm, 0, ~0); diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c index 2d3def024270..c1b9333f17eb 100644 --- a/arch/riscv/kvm/mmu.c +++ b/arch/riscv/kvm/mmu.c @@ -558,7 +558,8 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm) struct kvm_gstage gstage; void *pgd = NULL; - spin_lock(&kvm->mmu_lock); + lockdep_assert_held(&kvm->mmu_lock); + if (kvm->arch.pgd) { kvm_riscv_gstage_init(&gstage, kvm); kvm_riscv_gstage_unmap_range(&gstage, 0UL, @@ -568,7 +569,6 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm) kvm->arch.pgd_phys = 0; kvm->arch.pgd_levels = 0; } - spin_unlock(&kvm->mmu_lock); if (pgd) free_pages((unsigned long)pgd, get_order(kvm_riscv_gstage_pgd_size)); diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c index a9f083feeb76..f704a64bfc48 100644 --- a/arch/riscv/kvm/vm.c +++ b/arch/riscv/kvm/vm.c @@ -38,7 +38,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) r = kvm_riscv_gstage_vmid_init(kvm); if (r) { + spin_lock(&kvm->mmu_lock); kvm_riscv_mmu_free_pgd(kvm); + spin_unlock(&kvm->mmu_lock); return r; } diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 892246204435..6e6f94046b3f 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -7352,7 +7352,7 @@ static void kvm_mmu_zap_all(struct kvm *kvm) LIST_HEAD(invalid_list); int ign; - write_lock(&kvm->mmu_lock); + lockdep_assert_held_write(&kvm->mmu_lock); restart: list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) { if (WARN_ON_ONCE(sp->role.invalid)) @@ -7367,8 +7367,6 @@ static void kvm_mmu_zap_all(struct kvm *kvm) if (tdp_mmu_enabled) kvm_tdp_mmu_zap_all(kvm); - - write_unlock(&kvm->mmu_lock); } void kvm_arch_flush_shadow_all(struct kvm *kvm) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 89489996fbc1..f5affd3bfda8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -340,7 +340,10 @@ void kvm_flush_remote_tlbs_memslot(struct kvm *kvm, static void kvm_flush_shadow_all(struct kvm *kvm) { + KVM_MMU_LOCK(kvm); kvm_arch_flush_shadow_all(kvm); + KVM_MMU_UNLOCK(kvm); + kvm_arch_guest_memory_reclaimed(kvm); } -- 2.54.0.545.g6539524ca2-goog