[PATCH v2 1/2] RISCV: KVM: Introduce mp_state_lock to avoid lock inversion in SBI_EXT_HSM_HART_START
Yong-Xuan Wang
yongxuan.wang at sifive.com
Wed Apr 17 00:45:25 PDT 2024
Documentation/virt/kvm/locking.rst advises that kvm->lock should be
acquired outside vcpu->mutex and kvm->srcu. However, when KVM/RISC-V
handling SBI_EXT_HSM_HART_START, the lock ordering is vcpu->mutex,
kvm->srcu then kvm->lock.
Although the lockdep checking no longer complains about this after commit
f0f44752f5f6 ("rcu: Annotate SRCU's update-side lockdep dependencies"),
it's necessary to replace kvm->lock with a new dedicated lock to ensure
only one hart can execute the SBI_EXT_HSM_HART_START call for the target
hart simultaneously.
Additionally, this patch also rename "power_off" to "mp_state" with two
possible values. The vcpu->mp_state_lock also protects the access of
vcpu->mp_state.
Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
---
arch/riscv/include/asm/kvm_host.h | 7 ++--
arch/riscv/kvm/vcpu.c | 56 ++++++++++++++++++++++++-------
arch/riscv/kvm/vcpu_sbi.c | 7 ++--
arch/riscv/kvm/vcpu_sbi_hsm.c | 23 ++++++++-----
4 files changed, 68 insertions(+), 25 deletions(-)
diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 484d04a92fa6..64d35a8c908c 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -252,8 +252,9 @@ struct kvm_vcpu_arch {
/* Cache pages needed to program page tables with spinlock held */
struct kvm_mmu_memory_cache mmu_page_cache;
- /* VCPU power-off state */
- bool power_off;
+ /* VCPU power state */
+ struct kvm_mp_state mp_state;
+ spinlock_t mp_state_lock;
/* Don't run the VCPU (blocked) */
bool pause;
@@ -375,7 +376,9 @@ void kvm_riscv_vcpu_flush_interrupts(struct kvm_vcpu *vcpu);
void kvm_riscv_vcpu_sync_interrupts(struct kvm_vcpu *vcpu);
bool kvm_riscv_vcpu_has_interrupts(struct kvm_vcpu *vcpu, u64 mask);
void kvm_riscv_vcpu_power_off(struct kvm_vcpu *vcpu);
+void __kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
+bool kvm_riscv_vcpu_stopped(struct kvm_vcpu *vcpu);
void kvm_riscv_vcpu_sbi_sta_reset(struct kvm_vcpu *vcpu);
void kvm_riscv_vcpu_record_steal_time(struct kvm_vcpu *vcpu);
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index b5ca9f2e98ac..70937f71c3c4 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -102,6 +102,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
struct kvm_cpu_context *cntx;
struct kvm_vcpu_csr *reset_csr = &vcpu->arch.guest_reset_csr;
+ spin_lock_init(&vcpu->arch.mp_state_lock);
+
/* Mark this VCPU never ran */
vcpu->arch.ran_atleast_once = false;
vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
@@ -201,7 +203,7 @@ void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
{
return (kvm_riscv_vcpu_has_interrupts(vcpu, -1UL) &&
- !vcpu->arch.power_off && !vcpu->arch.pause);
+ !kvm_riscv_vcpu_stopped(vcpu) && !vcpu->arch.pause);
}
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
@@ -429,26 +431,50 @@ bool kvm_riscv_vcpu_has_interrupts(struct kvm_vcpu *vcpu, u64 mask)
return kvm_riscv_vcpu_aia_has_interrupts(vcpu, mask);
}
-void kvm_riscv_vcpu_power_off(struct kvm_vcpu *vcpu)
+static void __kvm_riscv_vcpu_power_off(struct kvm_vcpu *vcpu)
{
- vcpu->arch.power_off = true;
+ vcpu->arch.mp_state.mp_state = KVM_MP_STATE_STOPPED;
kvm_make_request(KVM_REQ_SLEEP, vcpu);
kvm_vcpu_kick(vcpu);
}
-void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu)
+void kvm_riscv_vcpu_power_off(struct kvm_vcpu *vcpu)
+{
+ spin_lock(&vcpu->arch.mp_state_lock);
+ __kvm_riscv_vcpu_power_off(vcpu);
+ spin_unlock(&vcpu->arch.mp_state_lock);
+}
+
+void __kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu)
{
- vcpu->arch.power_off = false;
+ vcpu->arch.mp_state.mp_state = KVM_MP_STATE_RUNNABLE;
kvm_vcpu_wake_up(vcpu);
}
+void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu)
+{
+ spin_lock(&vcpu->arch.mp_state_lock);
+ __kvm_riscv_vcpu_power_on(vcpu);
+ spin_unlock(&vcpu->arch.mp_state_lock);
+}
+
+bool kvm_riscv_vcpu_stopped(struct kvm_vcpu *vcpu)
+{
+ bool ret;
+
+ spin_lock(&vcpu->arch.mp_state_lock);
+ ret = vcpu->arch.mp_state.mp_state == KVM_MP_STATE_STOPPED;
+ spin_unlock(&vcpu->arch.mp_state_lock);
+
+ return ret;
+}
+
int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
struct kvm_mp_state *mp_state)
{
- if (vcpu->arch.power_off)
- mp_state->mp_state = KVM_MP_STATE_STOPPED;
- else
- mp_state->mp_state = KVM_MP_STATE_RUNNABLE;
+ spin_lock(&vcpu->arch.mp_state_lock);
+ *mp_state = vcpu->arch.mp_state;
+ spin_unlock(&vcpu->arch.mp_state_lock);
return 0;
}
@@ -458,17 +484,21 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
{
int ret = 0;
+ spin_lock(&vcpu->arch.mp_state_lock);
+
switch (mp_state->mp_state) {
case KVM_MP_STATE_RUNNABLE:
- vcpu->arch.power_off = false;
+ vcpu->arch.mp_state.mp_state = KVM_MP_STATE_RUNNABLE;
break;
case KVM_MP_STATE_STOPPED:
- kvm_riscv_vcpu_power_off(vcpu);
+ __kvm_riscv_vcpu_power_off(vcpu);
break;
default:
ret = -EINVAL;
}
+ spin_unlock(&vcpu->arch.mp_state_lock);
+
return ret;
}
@@ -584,11 +614,11 @@ static void kvm_riscv_check_vcpu_requests(struct kvm_vcpu *vcpu)
if (kvm_check_request(KVM_REQ_SLEEP, vcpu)) {
kvm_vcpu_srcu_read_unlock(vcpu);
rcuwait_wait_event(wait,
- (!vcpu->arch.power_off) && (!vcpu->arch.pause),
+ (!kvm_riscv_vcpu_stopped(vcpu)) && (!vcpu->arch.pause),
TASK_INTERRUPTIBLE);
kvm_vcpu_srcu_read_lock(vcpu);
- if (vcpu->arch.power_off || vcpu->arch.pause) {
+ if (kvm_riscv_vcpu_stopped(vcpu) || vcpu->arch.pause) {
/*
* Awaken to handle a signal, request to
* sleep again later.
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 72a2ffb8dcd1..1851fc979bd2 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -138,8 +138,11 @@ void kvm_riscv_vcpu_sbi_system_reset(struct kvm_vcpu *vcpu,
unsigned long i;
struct kvm_vcpu *tmp;
- kvm_for_each_vcpu(i, tmp, vcpu->kvm)
- tmp->arch.power_off = true;
+ kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
+ spin_lock(&vcpu->arch.mp_state_lock);
+ tmp->arch.mp_state.mp_state = KVM_MP_STATE_STOPPED;
+ spin_unlock(&vcpu->arch.mp_state_lock);
+ }
kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
memset(&run->system_event, 0, sizeof(run->system_event));
diff --git a/arch/riscv/kvm/vcpu_sbi_hsm.c b/arch/riscv/kvm/vcpu_sbi_hsm.c
index 7dca0e9381d9..115a6c6525fd 100644
--- a/arch/riscv/kvm/vcpu_sbi_hsm.c
+++ b/arch/riscv/kvm/vcpu_sbi_hsm.c
@@ -18,12 +18,18 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
struct kvm_vcpu *target_vcpu;
unsigned long target_vcpuid = cp->a0;
+ int ret = 0;
target_vcpu = kvm_get_vcpu_by_id(vcpu->kvm, target_vcpuid);
if (!target_vcpu)
return SBI_ERR_INVALID_PARAM;
- if (!target_vcpu->arch.power_off)
- return SBI_ERR_ALREADY_AVAILABLE;
+
+ spin_lock(&target_vcpu->arch.mp_state_lock);
+
+ if (target_vcpu->arch.mp_state.mp_state != KVM_MP_STATE_STOPPED) {
+ ret = SBI_ERR_ALREADY_AVAILABLE;
+ goto out;
+ }
reset_cntx = &target_vcpu->arch.guest_reset_context;
/* start address */
@@ -34,14 +40,18 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
reset_cntx->a1 = cp->a2;
kvm_make_request(KVM_REQ_VCPU_RESET, target_vcpu);
- kvm_riscv_vcpu_power_on(target_vcpu);
+ __kvm_riscv_vcpu_power_on(target_vcpu);
+
+out:
+ spin_unlock(&target_vcpu->arch.mp_state_lock);
+
return 0;
}
static int kvm_sbi_hsm_vcpu_stop(struct kvm_vcpu *vcpu)
{
- if (vcpu->arch.power_off)
+ if (kvm_riscv_vcpu_stopped(vcpu))
return SBI_ERR_FAILURE;
kvm_riscv_vcpu_power_off(vcpu);
@@ -58,7 +68,7 @@ static int kvm_sbi_hsm_vcpu_get_status(struct kvm_vcpu *vcpu)
target_vcpu = kvm_get_vcpu_by_id(vcpu->kvm, target_vcpuid);
if (!target_vcpu)
return SBI_ERR_INVALID_PARAM;
- if (!target_vcpu->arch.power_off)
+ if (!kvm_riscv_vcpu_stopped(target_vcpu))
return SBI_HSM_STATE_STARTED;
else if (vcpu->stat.generic.blocking)
return SBI_HSM_STATE_SUSPENDED;
@@ -71,14 +81,11 @@ static int kvm_sbi_ext_hsm_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
{
int ret = 0;
struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
- struct kvm *kvm = vcpu->kvm;
unsigned long funcid = cp->a6;
switch (funcid) {
case SBI_EXT_HSM_HART_START:
- mutex_lock(&kvm->lock);
ret = kvm_sbi_hsm_vcpu_start(vcpu);
- mutex_unlock(&kvm->lock);
break;
case SBI_EXT_HSM_HART_STOP:
ret = kvm_sbi_hsm_vcpu_stop(vcpu);
--
2.17.1
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