From: Oliver Upton oliver.upton@linux.dev
commit 0acc7239c20a8401b8968c2adace8f7c9b0295ae upstream.
KVM/arm64 had the lock ordering backwards on vcpu->mutex and kvm->lock from the very beginning. One such example is the way vCPU resets are handled: the kvm->lock is acquired while handling a guest CPU_ON PSCI call.
Add a dedicated lock to serialize writes to kvm_vcpu_arch::{mp_state, reset_state}. Promote all accessors of mp_state to {READ,WRITE}_ONCE() as readers do not acquire the mp_state_lock. While at it, plug yet another race by taking the mp_state_lock in the KVM_SET_MP_STATE ioctl handler.
As changes to MP state are now guarded with a dedicated lock, drop the kvm->lock acquisition from the PSCI CPU_ON path. Similarly, move the reader of reset_state outside of the kvm->lock and instead protect it with the mp_state_lock. Note that writes to reset_state::reset have been demoted to regular stores as both readers and writers acquire the mp_state_lock.
While the kvm->lock inversion still exists in kvm_reset_vcpu(), at least now PSCI CPU_ON no longer depends on it for serializing vCPU reset.
Cc: stable@vger.kernel.org Tested-by: Jeremy Linton jeremy.linton@arm.com Signed-off-by: Oliver Upton oliver.upton@linux.dev Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20230327164747.2466958-2-oliver.upton@linux.dev Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/arm.c | 31 ++++++++++++++++++++++--------- arch/arm64/kvm/psci.c | 28 ++++++++++++++++------------ arch/arm64/kvm/reset.c | 9 +++++---- 4 files changed, 44 insertions(+), 25 deletions(-)
--- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -482,6 +482,7 @@ struct kvm_vcpu_arch {
/* vcpu power state */ struct kvm_mp_state mp_state; + spinlock_t mp_state_lock;
/* Cache some mmu pages needed inside spinlock regions */ struct kvm_mmu_memory_cache mmu_page_cache; --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -336,6 +336,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu { int err;
+ spin_lock_init(&vcpu->arch.mp_state_lock); + /* Force users to call KVM_ARM_VCPU_INIT */ vcpu->arch.target = -1; bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES); @@ -453,34 +455,41 @@ void kvm_arch_vcpu_put(struct kvm_vcpu * vcpu->cpu = -1; }
-void kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu) +static void __kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu) { - vcpu->arch.mp_state.mp_state = KVM_MP_STATE_STOPPED; + WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_STOPPED); kvm_make_request(KVM_REQ_SLEEP, vcpu); kvm_vcpu_kick(vcpu); }
+void kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu) +{ + spin_lock(&vcpu->arch.mp_state_lock); + __kvm_arm_vcpu_power_off(vcpu); + spin_unlock(&vcpu->arch.mp_state_lock); +} + bool kvm_arm_vcpu_stopped(struct kvm_vcpu *vcpu) { - return vcpu->arch.mp_state.mp_state == KVM_MP_STATE_STOPPED; + return READ_ONCE(vcpu->arch.mp_state.mp_state) == KVM_MP_STATE_STOPPED; }
static void kvm_arm_vcpu_suspend(struct kvm_vcpu *vcpu) { - vcpu->arch.mp_state.mp_state = KVM_MP_STATE_SUSPENDED; + WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_SUSPENDED); kvm_make_request(KVM_REQ_SUSPEND, vcpu); kvm_vcpu_kick(vcpu); }
static bool kvm_arm_vcpu_suspended(struct kvm_vcpu *vcpu) { - return vcpu->arch.mp_state.mp_state == KVM_MP_STATE_SUSPENDED; + return READ_ONCE(vcpu->arch.mp_state.mp_state) == KVM_MP_STATE_SUSPENDED; }
int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu, struct kvm_mp_state *mp_state) { - *mp_state = vcpu->arch.mp_state; + *mp_state = READ_ONCE(vcpu->arch.mp_state);
return 0; } @@ -490,12 +499,14 @@ int kvm_arch_vcpu_ioctl_set_mpstate(stru { int ret = 0;
+ spin_lock(&vcpu->arch.mp_state_lock); + switch (mp_state->mp_state) { case KVM_MP_STATE_RUNNABLE: - vcpu->arch.mp_state = *mp_state; + WRITE_ONCE(vcpu->arch.mp_state, *mp_state); break; case KVM_MP_STATE_STOPPED: - kvm_arm_vcpu_power_off(vcpu); + __kvm_arm_vcpu_power_off(vcpu); break; case KVM_MP_STATE_SUSPENDED: kvm_arm_vcpu_suspend(vcpu); @@ -504,6 +515,8 @@ int kvm_arch_vcpu_ioctl_set_mpstate(stru ret = -EINVAL; }
+ spin_unlock(&vcpu->arch.mp_state_lock); + return ret; }
@@ -1223,7 +1236,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init if (test_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features)) kvm_arm_vcpu_power_off(vcpu); else - vcpu->arch.mp_state.mp_state = KVM_MP_STATE_RUNNABLE; + WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_RUNNABLE);
return 0; } --- a/arch/arm64/kvm/psci.c +++ b/arch/arm64/kvm/psci.c @@ -62,6 +62,7 @@ static unsigned long kvm_psci_vcpu_on(st struct vcpu_reset_state *reset_state; struct kvm *kvm = source_vcpu->kvm; struct kvm_vcpu *vcpu = NULL; + int ret = PSCI_RET_SUCCESS; unsigned long cpu_id;
cpu_id = smccc_get_arg1(source_vcpu); @@ -76,11 +77,15 @@ static unsigned long kvm_psci_vcpu_on(st */ if (!vcpu) return PSCI_RET_INVALID_PARAMS; + + spin_lock(&vcpu->arch.mp_state_lock); if (!kvm_arm_vcpu_stopped(vcpu)) { if (kvm_psci_version(source_vcpu) != KVM_ARM_PSCI_0_1) - return PSCI_RET_ALREADY_ON; + ret = PSCI_RET_ALREADY_ON; else - return PSCI_RET_INVALID_PARAMS; + ret = PSCI_RET_INVALID_PARAMS; + + goto out_unlock; }
reset_state = &vcpu->arch.reset_state; @@ -96,7 +101,7 @@ static unsigned long kvm_psci_vcpu_on(st */ reset_state->r0 = smccc_get_arg3(source_vcpu);
- WRITE_ONCE(reset_state->reset, true); + reset_state->reset = true; kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
/* @@ -108,7 +113,9 @@ static unsigned long kvm_psci_vcpu_on(st vcpu->arch.mp_state.mp_state = KVM_MP_STATE_RUNNABLE; kvm_vcpu_wake_up(vcpu);
- return PSCI_RET_SUCCESS; +out_unlock: + spin_unlock(&vcpu->arch.mp_state_lock); + return ret; }
static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu) @@ -168,8 +175,11 @@ static void kvm_prepare_system_event(str * after this call is handled and before the VCPUs have been * re-initialized. */ - kvm_for_each_vcpu(i, tmp, vcpu->kvm) - tmp->arch.mp_state.mp_state = KVM_MP_STATE_STOPPED; + kvm_for_each_vcpu(i, tmp, vcpu->kvm) { + spin_lock(&tmp->arch.mp_state_lock); + WRITE_ONCE(tmp->arch.mp_state.mp_state, KVM_MP_STATE_STOPPED); + spin_unlock(&tmp->arch.mp_state_lock); + } kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event)); @@ -229,7 +239,6 @@ static unsigned long kvm_psci_check_allo
static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) { - struct kvm *kvm = vcpu->kvm; u32 psci_fn = smccc_get_function(vcpu); unsigned long val; int ret = 1; @@ -254,9 +263,7 @@ static int kvm_psci_0_2_call(struct kvm_ kvm_psci_narrow_to_32bit(vcpu); fallthrough; case PSCI_0_2_FN64_CPU_ON: - mutex_lock(&kvm->lock); val = kvm_psci_vcpu_on(vcpu); - mutex_unlock(&kvm->lock); break; case PSCI_0_2_FN_AFFINITY_INFO: kvm_psci_narrow_to_32bit(vcpu); @@ -395,7 +402,6 @@ static int kvm_psci_1_x_call(struct kvm_
static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu) { - struct kvm *kvm = vcpu->kvm; u32 psci_fn = smccc_get_function(vcpu); unsigned long val;
@@ -405,9 +411,7 @@ static int kvm_psci_0_1_call(struct kvm_ val = PSCI_RET_SUCCESS; break; case KVM_PSCI_FN_CPU_ON: - mutex_lock(&kvm->lock); val = kvm_psci_vcpu_on(vcpu); - mutex_unlock(&kvm->lock); break; default: val = PSCI_RET_NOT_SUPPORTED; --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -255,15 +255,16 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu
mutex_lock(&vcpu->kvm->lock); ret = kvm_set_vm_width(vcpu); - if (!ret) { - reset_state = vcpu->arch.reset_state; - WRITE_ONCE(vcpu->arch.reset_state.reset, false); - } mutex_unlock(&vcpu->kvm->lock);
if (ret) return ret;
+ spin_lock(&vcpu->arch.mp_state_lock); + reset_state = vcpu->arch.reset_state; + vcpu->arch.reset_state.reset = false; + spin_unlock(&vcpu->arch.mp_state_lock); + /* Reset PMU outside of the non-preemptible section */ kvm_pmu_vcpu_reset(vcpu);