On 07/12/15 15:05, Marc Zyngier wrote:

On 03/12/15 06:11, Shannon Zhao wrote:

quoted

From: Shannon Zhao <redacted>

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.

Since this only supports ARM64 (or PMUv3), add a separate config symbol
for it.

Signed-off-by: Shannon Zhao <redacted>
---
 arch/arm64/include/asm/kvm_host.h |  2 ++
 arch/arm64/kvm/Kconfig            |  8 ++++++++
 include/kvm/arm_pmu.h             | 41 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+)
 create mode 100644 include/kvm/arm_pmu.h

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a35ce72..42e15bb 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h

@@ -37,6 +37,7 @@
 
 #include <kvm/arm_vgic.h>
 #include <kvm/arm_arch_timer.h>
+#include <kvm/arm_pmu.h>
 
 #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS
 

@@ -132,6 +133,7 @@ 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/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index a5272c0..66da9a2 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig

@@ -36,6 +36,7 @@ config KVM
 	select HAVE_KVM_EVENTFD
 	select HAVE_KVM_IRQFD
 	select KVM_ARM_VGIC_V3
+	select KVM_ARM_PMU
 	---help---
 	  Support hosting virtualized guest machines.
 	  We don't support KVM with 16K page tables yet, due to the multiple

@@ -48,6 +49,13 @@ config KVM_ARM_HOST
 	---help---
 	  Provides host support for ARM processors.
 
+config KVM_ARM_PMU
+	bool
+	depends on KVM_ARM_HOST && HW_PERF_EVENTS
+	---help---
+	  Adds support for a virtual Performance Monitoring Unit (PMU) in
+	  virtual machines.
+
 source drivers/vhost/Kconfig
 
 endif # VIRTUALIZATION

diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
new file mode 100644
index 0000000..0c13470
--- /dev/null
+++ b/include/kvm/arm_pmu.h

@@ -0,0 +1,41 @@
+/*
+ * 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 <linux/perf_event.h>
+#ifdef CONFIG_KVM_ARM_PMU
+#include <asm/pmu.h>
+#endif
+
+struct kvm_pmc {
+	u8 idx;/* index into the pmu->pmc array */
+	struct perf_event *perf_event;
+	struct kvm_vcpu *vcpu;

Why do you need this? If you have the pointer to a kvm_pmc structure, it
is very cheap to compute the address of the vcpu:

static inline kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
{
	struct kvm_pmu *pmu;
	pmc -= pmc->idx;
	pmu = container_of(pmc, struct kvm_pmu, pmc);
	return container_of(pmu, struct kvm_vcpu, pmu);
}

All of which the compiler will happily optimize for you.

FWIW, actually compiling code looks something like this:

static inline struct kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
{
	struct kvm_pmu *pmu;
	struct kvm_vcpu_arch *vcpu_arch;

	pmc -= pmc->idx;
	pmu = container_of(pmc, struct kvm_pmu, pmc[0]);
	vcpu_arch = container_of(pmu, struct kvm_vcpu_arch, pmu);
	return container_of(vcpu_arch, struct kvm_vcpu, arch);
}

which amounts to 4 sub instructions.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...