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Peter Anvin" , x86@kernel.org, Maxim Levitsky , Randy Dunlap , Paolo Bonzini , Will Deacon , Oliver Upton , Kunkun Jiang , Jing Zhang , Albert Ou , Keisuke Nishimura , Anup Patel , Catalin Marinas , Atish Patra , kvmarm@lists.linux.dev, Waiman Long , Boqun Feng , linux-arm-kernel@lists.infradead.org, Peter Zijlstra , Dave Hansen , Paul Walmsley , Suzuki K Poulose , Zenghui Yu , Sebastian Ott , Andre Przywara , Ingo Molnar , Alexandre Ghiti , Bjorn Helgaas , Palmer Dabbelt , Joey Gouly , Borislav Petkov , Sean Christopherson , Marc Zyngier , Alexander Potapenko , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Shusen Li , kvm-riscv@lists.infradead.org Subject: [PATCH v3 1/4] arm64: KVM: use mutex_trylock_nest_lock when locking all vCPUs Date: Wed, 30 Apr 2025 16:23:08 -0400 Message-ID: <20250430202311.364641-2-mlevitsk@redhat.com> In-Reply-To: <20250430202311.364641-1-mlevitsk@redhat.com> References: <20250430202311.364641-1-mlevitsk@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250430_132341_314515_479314B1 X-CRM114-Status: GOOD ( 24.87 ) 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 Use mutex_trylock_nest_lock instead of mutex_trylock when locking all vCPUs of a VM, to avoid triggering a lockdep warning, if the VM is configured to have more than MAX_LOCK_DEPTH vCPUs. This fixes the following false lockdep warning: [ 328.171264] BUG: MAX_LOCK_DEPTH too low! [ 328.175227] turning off the locking correctness validator. [ 328.180726] Please attach the output of /proc/lock_stat to the bug report [ 328.187531] depth: 48 max: 48! [ 328.190678] 48 locks held by qemu-kvm/11664: [ 328.194957] #0: ffff800086de5ba0 (&kvm->lock){+.+.}-{3:3}, at: kvm_ioctl_create_device+0x174/0x5b0 [ 328.204048] #1: ffff0800e78800b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.212521] #2: ffff07ffeee51e98 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.220991] #3: ffff0800dc7d80b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.229463] #4: ffff07ffe0c980b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.237934] #5: ffff0800a3883c78 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.246405] #6: ffff07fffbe480b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 Since the locking of all vCPUs is a primitive that can be useful in other architectures that are supported by KVM, also move the code to kvm_main.c Suggested-by: Paolo Bonzini Signed-off-by: Maxim Levitsky --- arch/arm64/include/asm/kvm_host.h | 3 -- arch/arm64/kvm/arch_timer.c | 4 +-- arch/arm64/kvm/arm.c | 43 --------------------------- arch/arm64/kvm/vgic/vgic-init.c | 4 +-- arch/arm64/kvm/vgic/vgic-its.c | 8 ++--- arch/arm64/kvm/vgic/vgic-kvm-device.c | 12 ++++---- include/linux/kvm_host.h | 3 ++ virt/kvm/kvm_main.c | 34 +++++++++++++++++++++ 8 files changed, 51 insertions(+), 60 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index e98cfe7855a6..96ce0b01a61e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1263,9 +1263,6 @@ int __init populate_sysreg_config(const struct sys_reg_desc *sr, unsigned int idx); int __init populate_nv_trap_config(void); -bool lock_all_vcpus(struct kvm *kvm); -void unlock_all_vcpus(struct kvm *kvm); - void kvm_calculate_traps(struct kvm_vcpu *vcpu); /* MMIO helpers */ diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c index 5133dcbfe9f7..fdbc8beec930 100644 --- a/arch/arm64/kvm/arch_timer.c +++ b/arch/arm64/kvm/arch_timer.c @@ -1766,7 +1766,7 @@ int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm, mutex_lock(&kvm->lock); - if (lock_all_vcpus(kvm)) { + if (!kvm_trylock_all_vcpus(kvm)) { set_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET, &kvm->arch.flags); /* @@ -1778,7 +1778,7 @@ int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm, kvm->arch.timer_data.voffset = offset->counter_offset; kvm->arch.timer_data.poffset = offset->counter_offset; - unlock_all_vcpus(kvm); + kvm_unlock_all_vcpus(kvm); } else { ret = -EBUSY; } diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 68fec8c95fee..d31f42a71bdc 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1914,49 +1914,6 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) } } -/* unlocks vcpus from @vcpu_lock_idx and smaller */ -static void unlock_vcpus(struct kvm *kvm, int vcpu_lock_idx) -{ - struct kvm_vcpu *tmp_vcpu; - - for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) { - tmp_vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx); - mutex_unlock(&tmp_vcpu->mutex); - } -} - -void unlock_all_vcpus(struct kvm *kvm) -{ - lockdep_assert_held(&kvm->lock); - - unlock_vcpus(kvm, atomic_read(&kvm->online_vcpus) - 1); -} - -/* Returns true if all vcpus were locked, false otherwise */ -bool lock_all_vcpus(struct kvm *kvm) -{ - struct kvm_vcpu *tmp_vcpu; - unsigned long c; - - lockdep_assert_held(&kvm->lock); - - /* - * Any time a vcpu is in an ioctl (including running), the - * core KVM code tries to grab the vcpu->mutex. - * - * By grabbing the vcpu->mutex of all VCPUs we ensure that no - * other VCPUs can fiddle with the state while we access it. - */ - kvm_for_each_vcpu(c, tmp_vcpu, kvm) { - if (!mutex_trylock(&tmp_vcpu->mutex)) { - unlock_vcpus(kvm, c - 1); - return false; - } - } - - return true; -} - static unsigned long nvhe_percpu_size(void) { return (unsigned long)CHOOSE_NVHE_SYM(__per_cpu_end) - diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index 1f33e71c2a73..6a426d403a6b 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -88,7 +88,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type) lockdep_assert_held(&kvm->lock); ret = -EBUSY; - if (!lock_all_vcpus(kvm)) + if (kvm_trylock_all_vcpus(kvm)) return ret; mutex_lock(&kvm->arch.config_lock); @@ -142,7 +142,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type) out_unlock: mutex_unlock(&kvm->arch.config_lock); - unlock_all_vcpus(kvm); + kvm_unlock_all_vcpus(kvm); return ret; } diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c index fb96802799c6..7454388e3646 100644 --- a/arch/arm64/kvm/vgic/vgic-its.c +++ b/arch/arm64/kvm/vgic/vgic-its.c @@ -1999,7 +1999,7 @@ static int vgic_its_attr_regs_access(struct kvm_device *dev, mutex_lock(&dev->kvm->lock); - if (!lock_all_vcpus(dev->kvm)) { + if (kvm_trylock_all_vcpus(dev->kvm)) { mutex_unlock(&dev->kvm->lock); return -EBUSY; } @@ -2034,7 +2034,7 @@ static int vgic_its_attr_regs_access(struct kvm_device *dev, } out: mutex_unlock(&dev->kvm->arch.config_lock); - unlock_all_vcpus(dev->kvm); + kvm_unlock_all_vcpus(dev->kvm); mutex_unlock(&dev->kvm->lock); return ret; } @@ -2704,7 +2704,7 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr) mutex_lock(&kvm->lock); - if (!lock_all_vcpus(kvm)) { + if (kvm_trylock_all_vcpus(kvm)) { mutex_unlock(&kvm->lock); return -EBUSY; } @@ -2726,7 +2726,7 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr) mutex_unlock(&its->its_lock); mutex_unlock(&kvm->arch.config_lock); - unlock_all_vcpus(kvm); + kvm_unlock_all_vcpus(kvm); mutex_unlock(&kvm->lock); return ret; } diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c index 359094f68c23..f9ae790163fb 100644 --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c @@ -268,7 +268,7 @@ static int vgic_set_common_attr(struct kvm_device *dev, return -ENXIO; mutex_lock(&dev->kvm->lock); - if (!lock_all_vcpus(dev->kvm)) { + if (kvm_trylock_all_vcpus(dev->kvm)) { mutex_unlock(&dev->kvm->lock); return -EBUSY; } @@ -276,7 +276,7 @@ static int vgic_set_common_attr(struct kvm_device *dev, mutex_lock(&dev->kvm->arch.config_lock); r = vgic_v3_save_pending_tables(dev->kvm); mutex_unlock(&dev->kvm->arch.config_lock); - unlock_all_vcpus(dev->kvm); + kvm_unlock_all_vcpus(dev->kvm); mutex_unlock(&dev->kvm->lock); return r; } @@ -390,7 +390,7 @@ static int vgic_v2_attr_regs_access(struct kvm_device *dev, mutex_lock(&dev->kvm->lock); - if (!lock_all_vcpus(dev->kvm)) { + if (kvm_trylock_all_vcpus(dev->kvm)) { mutex_unlock(&dev->kvm->lock); return -EBUSY; } @@ -415,7 +415,7 @@ static int vgic_v2_attr_regs_access(struct kvm_device *dev, out: mutex_unlock(&dev->kvm->arch.config_lock); - unlock_all_vcpus(dev->kvm); + kvm_unlock_all_vcpus(dev->kvm); mutex_unlock(&dev->kvm->lock); if (!ret && !is_write) @@ -554,7 +554,7 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev, mutex_lock(&dev->kvm->lock); - if (!lock_all_vcpus(dev->kvm)) { + if (kvm_trylock_all_vcpus(dev->kvm)) { mutex_unlock(&dev->kvm->lock); return -EBUSY; } @@ -611,7 +611,7 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev, out: mutex_unlock(&dev->kvm->arch.config_lock); - unlock_all_vcpus(dev->kvm); + kvm_unlock_all_vcpus(dev->kvm); mutex_unlock(&dev->kvm->lock); if (!ret && uaccess && !is_write) { diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 1dedc421b3e3..10d6652c7aa0 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1015,6 +1015,9 @@ static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id) void kvm_destroy_vcpus(struct kvm *kvm); +int kvm_trylock_all_vcpus(struct kvm *kvm); +void kvm_unlock_all_vcpus(struct kvm *kvm); + void vcpu_load(struct kvm_vcpu *vcpu); void vcpu_put(struct kvm_vcpu *vcpu); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 69782df3617f..834f08dfa24c 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1368,6 +1368,40 @@ static int kvm_vm_release(struct inode *inode, struct file *filp) return 0; } +/* + * Try to lock all of the VM's vCPUs. + * Assumes that the kvm->lock is held. + */ +int kvm_trylock_all_vcpus(struct kvm *kvm) +{ + struct kvm_vcpu *vcpu; + unsigned long i, j; + + kvm_for_each_vcpu(i, vcpu, kvm) + if (!mutex_trylock_nest_lock(&vcpu->mutex, &kvm->lock)) + goto out_unlock; + return 0; + +out_unlock: + kvm_for_each_vcpu(j, vcpu, kvm) { + if (i == j) + break; + mutex_unlock(&vcpu->mutex); + } + return -EINTR; +} +EXPORT_SYMBOL_GPL(kvm_trylock_all_vcpus); + +void kvm_unlock_all_vcpus(struct kvm *kvm) +{ + struct kvm_vcpu *vcpu; + unsigned long i; + + kvm_for_each_vcpu(i, vcpu, kvm) + mutex_unlock(&vcpu->mutex); +} +EXPORT_SYMBOL_GPL(kvm_unlock_all_vcpus); + /* * Allocation size is twice as large as the actual dirty bitmap size. * See kvm_vm_ioctl_get_dirty_log() why this is needed. -- 2.46.0