This patch enables running intensive I/O workloads, e.g. netperf, in a guest
deployed on a RT host. No change for !RT kernels.
The openpic spinlock becomes a sleeping mutex on a RT system. This no longer
guarantees that EPR is atomic with exception delivery. The guest VCPU thread
fails due to a BUG_ON(preemptible()) when running netperf.
In order to make the kvmppc_mpic_set_epr() call safe on RT from non-atomic
context, convert the openpic lock to a raw_spinlock. A similar approach can
be seen for x86 platforms in the following commit [1].
Here are some comparative cyclitest measurements run inside a high priority RT
guest run on a RT host. The guest has 1 VCPU and the test has been run for 15
minutes. The guest runs ~750 hackbench processes as background stress.
spinlock raw_spinlock
Min latency (us) 4 4
Avg latency (us) 1519
Max latency (us) 7062
[1] https://lkml.org/lkml/2010/1/11/289
Signed-off-by: Bogdan Purcareata bogdan.purcare...@freescale.com
---
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 2861ae9..309036c 100644
--- a/arch/powerpc/kvm/mpic.c
+++ b/arch/powerpc/kvm/mpic.c
@@ -194,7 +194,7 @@ struct openpic {
int num_mmio_regions;
gpa_t reg_base;
- spinlock_t lock;
+ raw_spinlock_t lock;
/* Behavior control */
struct fsl_mpic_info *fsl;
@@ -1105,9 +1105,9 @@ 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;
}
@@ -1182,12 +1182,12 @@ 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,
@@ -1387,9 +1387,9 @@ static int kvm_mpic_read(struct kvm_io_device *this,
gpa_t addr,
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_io_device *this,
gpa_t addr,
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;
@@ -1669,7 +1669,7
