Subject: [PATCH 02/18] KVM: ARM64: Add initial support for PMU

From: [email-masked] (Shannon Zhao)
Date: Fri, 17 Jul 2015 19:34:58 +0800

On 2015/7/17 17:58, Christoffer Dall wrote:
> On Fri, Jul 17, 2015 at 04:13:35PM +0800, Shannon Zhao wrote:
>>
>>
>> On 2015/7/17 2:25, Christoffer Dall wrote:
>>> On Mon, Jul 06, 2015 at 10:17:32AM +0800, shannon.zhao at linaro.org wrote:
>>>> From: Shannon Zhao <[email-masked]>
>>>>
>>>> Here we plan to support virtual PMU for guest by full software
>>>> emulation, so define some basic structs and functions preparing for
>>>> futher steps. Define struct kvm_pmc for performance monitor counter and
>>>> struct kvm_pmu for performance monitor unit for each vcpu. According to
>>>> ARMv8 spec, the PMU contains at most 32(ARMV8_MAX_COUNTERS) counters.
>>>> Initialize PMU for each vcpu when kvm initialize vcpus, while reset PMU
>>>> when kvm reset vcpus.
>>>> Since this only supports ARM64 (or PMUv3), add a separate config symbol
>>>> for it.
>>>>
>>>> Signed-off-by: Shannon Zhao <[email-masked]>
>>>> ---
>>>>   arch/arm/kvm/arm.c                |  4 +++
>>>>   arch/arm64/include/asm/kvm_host.h |  2 ++
>>>>   arch/arm64/include/asm/pmu.h      |  2 ++
>>>>   arch/arm64/kvm/Kconfig            |  7 +++++
>>>>   arch/arm64/kvm/Makefile           |  1 +
>>>>   arch/arm64/kvm/reset.c            |  3 +++
>>>>   include/kvm/arm_pmu.h             | 54 ++++++++++++++++++++++++++++++++++++++
>>>>   virt/kvm/arm/pmu.c                | 55 +++++++++++++++++++++++++++++++++++++++
>>>>   8 files changed, 128 insertions(+)
>>>>   create mode 100644 include/kvm/arm_pmu.h
>>>>   create mode 100644 virt/kvm/arm/pmu.c
>>>>
>>>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>>>> index bc738d2..4e82625 100644
>>>> --- a/arch/arm/kvm/arm.c
>>>> +++ b/arch/arm/kvm/arm.c
>>>> @@ -28,6 +28,7 @@
>>>>   #include <linux/sched.h>
>>>>   #include <linux/kvm.h>
>>>>   #include <trace/events/kvm.h>
>>>> +#include <kvm/arm_pmu.h>
>>>>
>>>>   #define CREATE_TRACE_POINTS
>>>>   #include "trace.h"
>>>> @@ -278,6 +279,9 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
>>>>   	/* Set up the timer */
>>>>   	kvm_timer_vcpu_init(vcpu);
>>>>
>>>> +	/* Set up the PMU */
>>>> +	kvm_pmu_init(vcpu);
>>>> +
>>>>   	return 0;
>>>>   }
>>>>
>>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>>>> index 2709db2..3c88873 100644
>>>> --- a/arch/arm64/include/asm/kvm_host.h
>>>> +++ b/arch/arm64/include/asm/kvm_host.h
>>>> @@ -42,6 +42,7 @@
>>>>
>>>>   #include <kvm/arm_vgic.h>
>>>>   #include <kvm/arm_arch_timer.h>
>>>> +#include <kvm/arm_pmu.h>
>>>>
>>>>   #define KVM_VCPU_MAX_FEATURES 3
>>>>
>>>> @@ -116,6 +117,7 @@ struct kvm_vcpu_arch {
>>>>   	/* VGIC state */
>>>>   	struct vgic_cpu vgic_cpu;
>>>>   	struct arch_timer_cpu timer_cpu;
>>>> +	struct kvm_pmu pmu;
>>>>
>>>>   	/*
>>>>   	 * Anything that is not used directly from assembly code goes
>>>> diff --git a/arch/arm64/include/asm/pmu.h b/arch/arm64/include/asm/pmu.h
>>>> index b9f394a..95681e6 100644
>>>> --- a/arch/arm64/include/asm/pmu.h
>>>> +++ b/arch/arm64/include/asm/pmu.h
>>>> @@ -19,6 +19,8 @@
>>>>   #ifndef __ASM_PMU_H
>>>>   #define __ASM_PMU_H
>>>>
>>>> +#include <linux/perf_event.h>
>>>> +
>>>>   #define ARMV8_MAX_COUNTERS      32
>>>>   #define ARMV8_COUNTER_MASK      (ARMV8_MAX_COUNTERS - 1)
>>>>
>>>> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
>>>> index bfffe8f..eae3a1b 100644
>>>> --- a/arch/arm64/kvm/Kconfig
>>>> +++ b/arch/arm64/kvm/Kconfig
>>>> @@ -31,6 +31,7 @@ config KVM
>>>>   	select KVM_VFIO
>>>>   	select HAVE_KVM_EVENTFD
>>>>   	select HAVE_KVM_IRQFD
>>>> +	select KVM_ARM_PMU
>>>>   	---help---
>>>>   	  Support hosting virtualized guest machines.
>>>>
>>>> @@ -52,4 +53,10 @@ config KVM_ARM_MAX_VCPUS
>>>>   	  large, so only choose a reasonable number that you expect to
>>>>   	  actually use.
>>>>
>>>> +config KVM_ARM_PMU
>>>> +	bool
>>>> +	depends on KVM_ARM_HOST
>>>> +	---help---
>>>> +	  Adds support for the Performance Monitoring in virtual machines.
>>>
>>> Adds support for a virtual Performance Monitoring Unit (PMU) in virtual
>>> machines.
>>>
>>>> +
>>>>   endif # VIRTUALIZATION
>>>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>>>> index f90f4aa..78db4ee 100644
>>>> --- a/arch/arm64/kvm/Makefile
>>>> +++ b/arch/arm64/kvm/Makefile
>>>> @@ -27,3 +27,4 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic-v3.o
>>>>   kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic-v3-emul.o
>>>>   kvm-$(CONFIG_KVM_ARM_HOST) += vgic-v3-switch.o
>>>>   kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arch_timer.o
>>>> +kvm-$(CONFIG_KVM_ARM_PMU) += $(KVM)/arm/pmu.o
>>>> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
>>>> index 0b43265..ee2c2e9 100644
>>>> --- a/arch/arm64/kvm/reset.c
>>>> +++ b/arch/arm64/kvm/reset.c
>>>> @@ -107,5 +107,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
>>>>   	/* Reset timer */
>>>>   	kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
>>>>
>>>> +	/* Reset PMU */
>>>> +	kvm_pmu_vcpu_reset(vcpu);
>>>> +
>>>>   	return 0;
>>>>   }
>>>> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
>>>> new file mode 100644
>>>> index 0000000..27d14ca
>>>> --- /dev/null
>>>> +++ b/include/kvm/arm_pmu.h
>>>> @@ -0,0 +1,54 @@
>>>> +/*
>>>> + * Copyright (C) 2015 Linaro Ltd.
>>>> + * Author: Shannon Zhao <[email-masked]>
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License version 2 as
>>>> + * published by the Free Software Foundation.
>>>> + *
>>>> + * This program is distributed in the hope that it will be useful,
>>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>>> + * GNU General Public License for more details.
>>>> + *
>>>> + * You should have received a copy of the GNU General Public License
>>>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>>>> + */
>>>> +
>>>> +#ifndef __ASM_ARM_KVM_PMU_H
>>>> +#define __ASM_ARM_KVM_PMU_H
>>>> +
>>>> +#include <asm/pmu.h>
>>>> +#include <linux/irq_work.h>
>>>> +
>>>> +struct kvm_pmc {
>>>> +	u8 idx;
>>>
>>> which index is this?  Does it map to something architecturally or is it
>>> just the array index number?
>>>
>>
>> It's the index of the PMU counter.
>>
>
> sorry, I don't feel this answers my question? ;)
>

This index is only used for kvm_pmu_perf_overflow to locate the index of 
this PMU counter and kvm_pmu_perf_overflow will set the corresponding 
bit of overflow_status to show whether this counter overflows.

See patch 17/18:

+static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
+				  struct perf_sample_data *data,
+				  struct pt_regs *regs)
+{
+	struct kvm_pmc *pmc = perf_event->overflow_handler_context;
+	struct kvm_vcpu *vcpu = pmc->vcpu;
+	struct kvm_pmu *pmu = &vcpu->arch.pmu;
+
+	if (pmc->interrupt == true) {
+		__set_bit(pmc->idx, (unsigned long *)&pmu->overflow_status);

>>>> +	u64 counter;
>>>> +	u64 eventsel;
>>>
>>> does this map to PMEVTYPER<n>_EL0.evtCount?
>>>
>> No, it just stores the event type.
>>
>
> can you specify more clearly what this maps to/how I derive its meaning?
>
> Is this a perf (Linux) event type number, or an architecturally defined
> thing?
>

Yes, it stores a perf event type number. This is used for 
kvm_pmu_set_counter_event_type to check whether event type of this time 
is same with the previous one. If they are same, it will return and 
doesn't create a new perf event for it and just reuses the previous one.

See PATCH 07/18:

+void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, unsigned 
long data,
+				    unsigned long select_idx)
+{
+	struct kvm_pmu *pmu = &vcpu->arch.pmu;
+	struct kvm_pmc *pmc = &pmu->pmc[select_idx];
+	struct perf_event *event;
+	struct perf_event_attr attr;
+	unsigned config, type = PERF_TYPE_RAW;
+
+	if ((data & ARMV8_EVTYPE_EVENT) == pmc->eventsel)
+		return;

> Thanks,
> -Christoffer

-- 
Shannon