Messages in this thread |  | | Date | Tue, 17 Feb 2015 14:27:44 +0200 | From | Purcareata Bogdan <> | Subject | Re: [PATCH] KVM: PPC: Convert openpic lock to raw_spinlock |
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Ping?
On 02.02.2015 11:35, Purcareata Bogdan wrote: > Ping? > > On 22.01.2015 11:39, Bogdan Purcareata wrote: >> This patch enables running intensive I/O workloads, e.g. netperf, in a guest >> deployed on a RT host. It also enable guests to be SMP. >> >> 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) 15 19 >> Max latency (us) 70 62 >> >> Due to the introduction of the raw_spinlock, guests with a high number of VCPUs >> may induce great latencies on the underlying RT Linux system (e.g. cyclictest >> reports latencies of ~15ms for guests with 24 VCPUs). This can be further >> aggravated by sending a lot of external interrupts to the guest. A malicious app >> can abuse this scenario, causing a DoS of the host Linux. Until the KVM openpic >> code is refactored to use finer lock granularity, impose a limitation on the >> number of VCPUs a guest can have when running on a PREEMPT_RT_FULL system with >> KVM_MPIC emulation. >> >> Sent against v3.14-rt branch of >> git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git >> >> [1] https://lkml.org/lkml/2010/1/11/289 >> >> Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com> >> [ add KVM_MAX_VCPUS limitation ] >> Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> >> Reviewed-by: Scott Wood <scottwood@freescale.com> >> --- >> arch/powerpc/include/asm/kvm_host.h | 6 +++++ >> arch/powerpc/kvm/mpic.c | 44 ++++++++++++++++++------------------- >> 2 files changed, 28 insertions(+), 22 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h >> index 1eaea2d..5ae38c5 100644 >> --- a/arch/powerpc/include/asm/kvm_host.h >> +++ b/arch/powerpc/include/asm/kvm_host.h >> @@ -35,8 +35,14 @@ >> #include <asm/page.h> >> #include <asm/cacheflush.h> >> >> +#if defined(CONFIG_PREEMPT_RT_FULL) && defined(CONFIG_KVM_MPIC) >> +/* Limit the number of vcpus due to in-kernel mpic concurrency */ >> +#define KVM_MAX_VCPUS 4 >> +#define KVM_MAX_VCORES 4 >> +#else >> #define KVM_MAX_VCPUS NR_CPUS >> #define KVM_MAX_VCORES NR_CPUS >> +#endif >> #define KVM_USER_MEM_SLOTS 32 >> #define KVM_MEM_SLOTS_NUM KVM_USER_MEM_SLOTS >> >> diff --git a/arch/powerpc/kvm/mpic.c b/arch/powerpc/kvm/mpic.c >> index efbd996..b9802a3 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; >> @@ -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; >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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