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

[Christoffer Dall <christoffer.dall@linaro.org>]

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@linaro.org wrote:
> >> From: Shannon Zhao <shannon.zhao@linaro.org>
> >>
> >> 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 <shannon.zhao@linaro.org>
> >> ---
> >>  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 <shannon.zhao@linaro.org>
> >> + *
> >> + * 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? ;)

> >> +	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?


Thanks,
-Christoffer