The lock in the KVM openpic emulation on PPC is a spinlock_t, meaning it becomes
a sleeping mutex under PREEMPT_RT_FULL. This yields to a situation where this
non-raw lock is grabbed with interrupts already disabled by hard_irq_disable():
kvmppc_prepare_to_enter()
hard_irq_disable()
kvmppc_core_prepare_to_enter()
kvmppc_core_check_exceptions()
kvmppc_booke_irqprio_deliver()
kvmppc_mpic_set_epr()
spin_lock_irqsave()
...
This happens for guest interrupts that go through this openpic emulation code.
The result is a kernel crash on guest enter (include/linux/kvm_host.h:784).
Converting the lock to a raw_spinlock fixes the issue and enables the guest to
run I/O intensive workloads in a SMP configuration. A similar fix can be found
for the i8254 PIT emulation on x86 [1].
[1] https://lkml.org/lkml/2010/1/11/289
v2:
- updated commit message
Signed-off-by: Bogdan Purcareata <bogdan.purcareata@xxxxxxxxxxxxx>
---
arch/powerpc/kvm/mpic.c | 44 ++++++++++++++++++++++----------------------
1 file changed, 22 insertions(+), 22 deletions(-)
diff --git a/arch/powerpc/kvm/mpic.c b/arch/powerpc/kvm/mpic.c
index 6249cdc..2f70660 100644
--- a/arch/powerpc/kvm/mpic.c
+++ b/arch/powerpc/kvm/mpic.c
@@ -196,7 +196,7 @@ struct openpic {
int num_mmio_regions;
gpa_t reg_base;
- spinlock_t lock;
+ raw_spinlock_t lock;
/* Behavior control */
struct fsl_mpic_info *fsl;
@@ -1103,9 +1103,9 @@ static int openpic_cpu_write_internal(void *opaque, gpa_t addr,
mpic_irq_raise(opp, dst, ILR_INTTGT_INT);
}
- spin_unlock(&opp->lock);
+ raw_spin_unlock(&opp->lock);
kvm_notify_acked_irq(opp->kvm, 0, notify_eoi);
- spin_lock(&opp->lock);
+ raw_spin_lock(&opp->lock);
break;
}
@@ -1180,12 +1180,12 @@ void kvmppc_mpic_set_epr(struct kvm_vcpu *vcpu)
int cpu = vcpu->arch.irq_cpu_id;
unsigned long flags;
- spin_lock_irqsave(&opp->lock, flags);
+ raw_spin_lock_irqsave(&opp->lock, flags);
if ((opp->gcr & opp->mpic_mode_mask) == GCR_MODE_PROXY)
kvmppc_set_epr(vcpu, openpic_iack(opp, &opp->dst[cpu], cpu));
- spin_unlock_irqrestore(&opp->lock, flags);
+ raw_spin_unlock_irqrestore(&opp->lock, flags);
}
static int openpic_cpu_read_internal(void *opaque, gpa_t addr,
@@ -1386,9 +1386,9 @@ static int kvm_mpic_read(struct kvm_vcpu *vcpu,
return -EINVAL;
}
- spin_lock_irq(&opp->lock);
+ raw_spin_lock_irq(&opp->lock);
ret = kvm_mpic_read_internal(opp, addr - opp->reg_base, &u.val);
- spin_unlock_irq(&opp->lock);
+ raw_spin_unlock_irq(&opp->lock);
/*
* Technically only 32-bit accesses are allowed, but be nice to
@@ -1427,10 +1427,10 @@ static int kvm_mpic_write(struct kvm_vcpu *vcpu,
return -EOPNOTSUPP;
}
- spin_lock_irq(&opp->lock);
+ raw_spin_lock_irq(&opp->lock);
ret = kvm_mpic_write_internal(opp, addr - opp->reg_base,
*(const u32 *)ptr);
- spin_unlock_irq(&opp->lock);
+ raw_spin_unlock_irq(&opp->lock);
pr_debug("%s: addr %llx ret %d val %x\n",
__func__, addr, ret, *(const u32 *)ptr);
@@ -1501,14 +1501,14 @@ static int access_reg(struct openpic *opp, gpa_t addr, u32 *val, int type)
if (addr & 3)
return -ENXIO;
- spin_lock_irq(&opp->lock);
+ raw_spin_lock_irq(&opp->lock);
if (type == ATTR_SET)
ret = kvm_mpic_write_internal(opp, addr, *val);
else
ret = kvm_mpic_read_internal(opp, addr, val);
- spin_unlock_irq(&opp->lock);
+ raw_spin_unlock_irq(&opp->lock);
pr_debug("%s: type %d addr %llx val %x\n", __func__, type, addr, *val);
@@ -1545,9 +1545,9 @@ static int mpic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
if (attr32 != 0 && attr32 != 1)
return -EINVAL;
- spin_lock_irq(&opp->lock);
+ raw_spin_lock_irq(&opp->lock);
openpic_set_irq(opp, attr->attr, attr32);
- spin_unlock_irq(&opp->lock);
+ raw_spin_unlock_irq(&opp->lock);
return 0;
}
@@ -1592,9 +1592,9 @@ static int mpic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
if (attr->attr > MAX_SRC)
return -EINVAL;
- spin_lock_irq(&opp->lock);
+ raw_spin_lock_irq(&opp->lock);
attr32 = opp->src[attr->attr].pending;
- spin_unlock_irq(&opp->lock);
+ raw_spin_unlock_irq(&opp->lock);
if (put_user(attr32, (u32 __user *)(long)attr->addr))
return -EFAULT;
@@ -1670,7 +1670,7 @@ static int mpic_create(struct kvm_device *dev, u32 type)
opp->kvm = dev->kvm;
opp->dev = dev;
opp->model = type;
- spin_lock_init(&opp->lock);
+ raw_spin_lock_init(&opp->lock);
add_mmio_region(opp, &openpic_gbl_mmio);
add_mmio_region(opp, &openpic_tmr_mmio);
@@ -1743,7 +1743,7 @@ int kvmppc_mpic_connect_vcpu(struct kvm_device *dev, struct kvm_vcpu *vcpu,
if (cpu < 0 || cpu >= MAX_CPU)
return -EPERM;
- spin_lock_irq(&opp->lock);
+ raw_spin_lock_irq(&opp->lock);
if (opp->dst[cpu].vcpu) {
ret = -EEXIST;
@@ -1766,7 +1766,7 @@ int kvmppc_mpic_connect_vcpu(struct kvm_device *dev, struct kvm_vcpu *vcpu,
vcpu->arch.epr_flags |= KVMPPC_EPR_KERNEL;
out:
- spin_unlock_irq(&opp->lock);
+ raw_spin_unlock_irq(&opp->lock);
return ret;
}
@@ -1796,9 +1796,9 @@ static int mpic_set_irq(struct kvm_kernel_irq_routing_entry *e,
struct openpic *opp = kvm->arch.mpic;
unsigned long flags;
- spin_lock_irqsave(&opp->lock, flags);
+ raw_spin_lock_irqsave(&opp->lock, flags);
openpic_set_irq(opp, irq, level);
- spin_unlock_irqrestore(&opp->lock, flags);
+ raw_spin_unlock_irqrestore(&opp->lock, flags);
/* All code paths we care about don't check for the return value */
return 0;
@@ -1810,14 +1810,14 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
struct openpic *opp = kvm->arch.mpic;
unsigned long flags;
- spin_lock_irqsave(&opp->lock, flags);
+ raw_spin_lock_irqsave(&opp->lock, flags);
/*
* XXX We ignore the target address for now, as we only support
* a single MSI bank.
*/
openpic_msi_write(kvm->arch.mpic, MSIIR_OFFSET, e->msi.data);
- spin_unlock_irqrestore(&opp->lock, flags);
+ raw_spin_unlock_irqrestore(&opp->lock, flags);
/* All code paths we care about don't check for the return value */
return 0;
--
2.1.4
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