[Qemu-devel] [PATCH V8 0/2] Add option to configure guest vPMU

[Qemu-devel] [PATCH V8 0/2] Add option to configure guest vPMU

[Wei Huang]

This patchset adds a pmu=[on/off] option to enable/disable vPMU support 
for guest VM. There are several reasons to justify this option. First,
vPMU can be problematic for cross-migration between different SoC as perf
counters are architecture-dependent. It is more flexible to have an option
to turn it on/off. Secondly this option matches the "pmu" option as
supported in libvirt. To make sure backward compatible, a PMU-related
property is added to mach-virt machine types.

The following are testing results with this patchset:
 CONFIG (qemu-system-aarch64)                       vPMU   WARNING
  -M virt-2.8/virt,accel=kvm -cpu host               YES    NO
  -M virt-2.8/virt,accel=kvm -cpu host,pmu=off       NO     NO
  -M virt-2.8/virt,accel=kvm -cpu host,pmu=on        YES    NO
  -M virt-2.7,accel=kvm -cpu host                    YES    NO
  -M virt-2.7,accel=kvm -cpu host,pmu=off            NO     NO
  -M virt-2.7,accel=kvm -cpu host,pmu=on             YES    NO
  -M virt-2.6,accel=kvm -cpu host                    NO     NO
  -M virt-2.6,accel=kvm -cpu host,pmu=off            NO     NO
  -M virt-2.6,accel=kvm -cpu host,pmu=on             NO     NO

  -M virt-2.8/virt,accel=tcg -cpu cortex-a57         NO     NO
  -M virt-2.8/virt,accel=tcg -cpu cortex-a57,pmu=off NO     NO
  -M virt-2.8/virt,accel=tcg -cpu cortex-a57,pmu=on  NO     NO
  -M virt-2.7,accel=tcg -cpu cortex-a57              NO     NO
  -M virt-2.7,accel=tcg -cpu cortex-a57,pmu=off      NO     NO
  -M virt-2.7,accel=tcg -cpu cortex-a57,pmu=on       NO     NO
  -M virt-2.6,accel=tcg -cpu cortex-a57              NO     NO
  -M virt-2.6,accel=tcg -cpu cortex-a57,pmu=off      NO     NO
  -M virt-2.6,accel=tcg -cpu cortex-a57,pmu=on       NO     NO

  -M virt-2.8/virt,accel=tcg -cpu cortex-a15         NO     NO
  -M virt-2.8/virt,accel=tcg -cpu cortex-a15,pmu=off NO     "No PMU property"
  -M virt-2.8/virt,accel=tcg -cpu cortex-a15,pmu=on  NO     "No PMU property"
  -M virt-2.7,accel=tcg -cpu cortex-a15              NO     NO
  -M virt-2.7,accel=tcg -cpu cortex-a15,pmu=off      NO     "No PMU property"
  -M virt-2.7,accel=tcg -cpu cortex-a15,pmu=on       NO     "No PMU property"
  -M virt-2.6,accel=tcg -cpu cortex-a15              NO     NO
  -M virt-2.6,accel=tcg -cpu cortex-a15,pmu=off      NO     "No PMU property"
  -M virt-2.6,accel=tcg -cpu cortex-a15,pmu=on       NO     "No PMU property"

  * "No PMU property" msg
    can't apply global cortex-a15-arm-cpu.pmu=off: Property '.pmu' not found

V7->V8:
  * add back the "pmu" property for TCG mode

V6->V7:
  * change has_pmu variable type from OnOffAuto to Boolean
  * only add "pmu" property to CPU under kvm mode, default ON
  * set no_pmu=true for machvirt-2.6

V5->V6:
  * adapt patches for new machine type 2.8

V4->V5:
  * remove comment change for has_pmu
  * remove warning msg when pmu_default_on=TRUE && has_pmu=AUTO && tcg=TRUE

V3->V4:
  * change has_pmu from Boolean to OnOffAuto to handle different cases
  * "pmu" property is re-defined as DEFINE_PROP_ON_OFF_AUTO

V2->V3:
  * revise patch 1 commit msg and if-else statement (Drew) 
  * move property field into VirtMachineClass (Drew)

V1->V2:
  * keep the original field name as "has_pmu"
  * add a warning message when PMU is turned on without KVM
  * use the feature bit to check PMU availability, instead of using has_pmu
  * add PMU compat support to mach-virt machine type

RFC->V1:
  * set default pmu=off
  * change struct ARMCPU field name "has_pmu" ==> "has_host_pmu"
  * like el3, add a new feature ARM_FEATURE_HOST_PMU
  * "pmu" property becomes CPU dependent. Only cortex-a53/cortex-a57/host
    running on kvm supports this option.

Thanks,
-Wei

Wei Huang (2):
  arm: Add an option to turn on/off vPMU support
  arm: virt: add PMU property to mach-virt machine type

 hw/arm/virt-acpi-build.c |  2 +-
 hw/arm/virt.c            |  9 ++++++++-
 target-arm/cpu.c         | 15 +++++++++++++++
 target-arm/cpu.h         |  1 +
 target-arm/cpu64.c       |  2 ++
 target-arm/kvm64.c       | 17 ++++++++++++++---
 6 files changed, 41 insertions(+), 5 deletions(-)

-- 
1.8.3.1

[Qemu-devel] [PATCH V8 1/2] arm: Add an option to turn on/off vPMU support

[Wei Huang]

This patch adds a pmu=[on/off] option to enable/disable vPMU support
in guest vCPU. It allows virt tools, such as libvirt, to determine the
exsitence of vPMU and configure it. Note this option is only available
for cortex-a57/cortex-53/ host CPUs, but unavailable on ARMv7 and other
processors. Also even though "pmu=" option is available for TCG mode,
setting it doesn't turn PMU on.

Signed-off-by: Wei Huang <wei@redhat.com>
---
 hw/arm/virt-acpi-build.c |  2 +-
 hw/arm/virt.c            |  2 +-
 target-arm/cpu.c         | 15 +++++++++++++++
 target-arm/cpu.h         |  1 +
 target-arm/cpu64.c       |  2 ++
 target-arm/kvm64.c       | 17 ++++++++++++++---
 6 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index fa0655a..49898df 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -539,7 +539,7 @@ build_madt(GArray *table_data, BIOSLinker *linker, VirtGuestInfo *guest_info)
         gicc->uid = i;
         gicc->flags = cpu_to_le32(ACPI_GICC_ENABLED);
 
-        if (armcpu->has_pmu) {
+        if (arm_feature(&armcpu->env, ARM_FEATURE_PMU)) {
             gicc->performance_interrupt = cpu_to_le32(PPI(VIRTUAL_PMU_IRQ));
         }
     }
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 895446f..074d11c 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -490,7 +490,7 @@ static void fdt_add_pmu_nodes(const VirtBoardInfo *vbi, int gictype)
 
     CPU_FOREACH(cpu) {
         armcpu = ARM_CPU(cpu);
-        if (!armcpu->has_pmu ||
+        if (!arm_feature(&armcpu->env, ARM_FEATURE_PMU) ||
             !kvm_arm_pmu_create(cpu, PPI(VIRTUAL_PMU_IRQ))) {
             return;
         }
diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 1b9540e..655a1f8 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -19,6 +19,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "cpu.h"
 #include "internals.h"
@@ -509,6 +510,10 @@ static Property arm_cpu_rvbar_property =
 static Property arm_cpu_has_el3_property =
             DEFINE_PROP_BOOL("has_el3", ARMCPU, has_el3, true);
 
+/* use property name "pmu" to match other archs and virt tools */
+static Property arm_cpu_has_pmu_property =
+            DEFINE_PROP_BOOL("pmu", ARMCPU, has_pmu, true);
+
 static Property arm_cpu_has_mpu_property =
             DEFINE_PROP_BOOL("has-mpu", ARMCPU, has_mpu, true);
 
@@ -552,6 +557,11 @@ static void arm_cpu_post_init(Object *obj)
 #endif
     }
 
+    if (arm_feature(&cpu->env, ARM_FEATURE_PMU)) {
+        qdev_property_add_static(DEVICE(obj), &arm_cpu_has_pmu_property,
+                                 &error_abort);
+    }
+
     if (arm_feature(&cpu->env, ARM_FEATURE_MPU)) {
         qdev_property_add_static(DEVICE(obj), &arm_cpu_has_mpu_property,
                                  &error_abort);
@@ -648,6 +658,11 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
         cpu->id_aa64pfr0 &= ~0xf000;
     }
 
+    if (!cpu->has_pmu || !kvm_enabled()) {
+        cpu->has_pmu = false;
+        unset_feature(env, ARM_FEATURE_PMU);
+    }
+
     if (!arm_feature(env, ARM_FEATURE_EL2)) {
         /* Disable the hypervisor feature bits in the processor feature
          * registers if we don't have EL2. These are id_pfr1[15:12] and
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 2218c00..b97b93b 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -1129,6 +1129,7 @@ enum arm_features {
     ARM_FEATURE_V8_SHA256, /* implements SHA256 part of v8 Crypto Extensions */
     ARM_FEATURE_V8_PMULL, /* implements PMULL part of v8 Crypto Extensions */
     ARM_FEATURE_THUMB_DSP, /* DSP insns supported in the Thumb encodings */
+    ARM_FEATURE_PMU, /* has PMU support */
 };
 
 static inline int arm_feature(CPUARMState *env, int feature)
diff --git a/target-arm/cpu64.c b/target-arm/cpu64.c
index 1635deb..549cb1e 100644
--- a/target-arm/cpu64.c
+++ b/target-arm/cpu64.c
@@ -111,6 +111,7 @@ static void aarch64_a57_initfn(Object *obj)
     set_feature(&cpu->env, ARM_FEATURE_V8_PMULL);
     set_feature(&cpu->env, ARM_FEATURE_CRC);
     set_feature(&cpu->env, ARM_FEATURE_EL3);
+    set_feature(&cpu->env, ARM_FEATURE_PMU);
     cpu->kvm_target = QEMU_KVM_ARM_TARGET_CORTEX_A57;
     cpu->midr = 0x411fd070;
     cpu->revidr = 0x00000000;
@@ -166,6 +167,7 @@ static void aarch64_a53_initfn(Object *obj)
     set_feature(&cpu->env, ARM_FEATURE_V8_PMULL);
     set_feature(&cpu->env, ARM_FEATURE_CRC);
     set_feature(&cpu->env, ARM_FEATURE_EL3);
+    set_feature(&cpu->env, ARM_FEATURE_PMU);
     cpu->kvm_target = QEMU_KVM_ARM_TARGET_CORTEX_A53;
     cpu->midr = 0x410fd034;
     cpu->revidr = 0x00000000;
diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c
index 5faa76c..6111109 100644
--- a/target-arm/kvm64.c
+++ b/target-arm/kvm64.c
@@ -428,6 +428,11 @@ static inline void set_feature(uint64_t *features, int feature)
     *features |= 1ULL << feature;
 }
 
+static inline void unset_feature(uint64_t *features, int feature)
+{
+    *features &= ~(1ULL << feature);
+}
+
 bool kvm_arm_get_host_cpu_features(ARMHostCPUClass *ahcc)
 {
     /* Identify the feature bits corresponding to the host CPU, and
@@ -469,6 +474,7 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUClass *ahcc)
     set_feature(&features, ARM_FEATURE_VFP4);
     set_feature(&features, ARM_FEATURE_NEON);
     set_feature(&features, ARM_FEATURE_AARCH64);
+    set_feature(&features, ARM_FEATURE_PMU);
 
     ahcc->features = features;
 
@@ -482,6 +488,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
     int ret;
     uint64_t mpidr;
     ARMCPU *cpu = ARM_CPU(cs);
+    CPUARMState *env = &cpu->env;
 
     if (cpu->kvm_target == QEMU_KVM_ARM_TARGET_NONE ||
         !object_dynamic_cast(OBJECT(cpu), TYPE_AARCH64_CPU)) {
@@ -501,10 +508,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
     if (!arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
         cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_EL1_32BIT;
     }
-    if (kvm_irqchip_in_kernel() &&
-        kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PMU_V3)) {
-        cpu->has_pmu = true;
+    if (!kvm_irqchip_in_kernel() ||
+        !kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PMU_V3)) {
+            cpu->has_pmu = false;
+    }
+    if (cpu->has_pmu) {
         cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_PMU_V3;
+    } else {
+        unset_feature(&env->features, ARM_FEATURE_PMU);
     }
 
     /* Do KVM_ARM_VCPU_INIT ioctl */
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH V8 1/2] arm: Add an option to turn on/off vPMU support

[Andrew Jones]

On Wed, Oct 26, 2016 at 02:28:20AM -0400, Wei Huang wrote:
> This patch adds a pmu=[on/off] option to enable/disable vPMU support
> in guest vCPU. It allows virt tools, such as libvirt, to determine the
> exsitence of vPMU and configure it. Note this option is only available
> for cortex-a57/cortex-53/ host CPUs, but unavailable on ARMv7 and other
> processors. Also even though "pmu=" option is available for TCG mode,
> setting it doesn't turn PMU on.
> 
> Signed-off-by: Wei Huang <wei@redhat.com>
> ---
>  hw/arm/virt-acpi-build.c |  2 +-
>  hw/arm/virt.c            |  2 +-
>  target-arm/cpu.c         | 15 +++++++++++++++
>  target-arm/cpu.h         |  1 +
>  target-arm/cpu64.c       |  2 ++
>  target-arm/kvm64.c       | 17 ++++++++++++++---
>  6 files changed, 34 insertions(+), 5 deletions(-)

Reviewed-by: Andrew Jones <drjones@redhat.com>

> 
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index fa0655a..49898df 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -539,7 +539,7 @@ build_madt(GArray *table_data, BIOSLinker *linker, VirtGuestInfo *guest_info)
>          gicc->uid = i;
>          gicc->flags = cpu_to_le32(ACPI_GICC_ENABLED);
>  
> -        if (armcpu->has_pmu) {
> +        if (arm_feature(&armcpu->env, ARM_FEATURE_PMU)) {
>              gicc->performance_interrupt = cpu_to_le32(PPI(VIRTUAL_PMU_IRQ));
>          }
>      }
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 895446f..074d11c 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -490,7 +490,7 @@ static void fdt_add_pmu_nodes(const VirtBoardInfo *vbi, int gictype)
>  
>      CPU_FOREACH(cpu) {
>          armcpu = ARM_CPU(cpu);
> -        if (!armcpu->has_pmu ||
> +        if (!arm_feature(&armcpu->env, ARM_FEATURE_PMU) ||
>              !kvm_arm_pmu_create(cpu, PPI(VIRTUAL_PMU_IRQ))) {
>              return;
>          }
> diff --git a/target-arm/cpu.c b/target-arm/cpu.c
> index 1b9540e..655a1f8 100644
> --- a/target-arm/cpu.c
> +++ b/target-arm/cpu.c
> @@ -19,6 +19,7 @@
>   */
>  
>  #include "qemu/osdep.h"
> +#include "qemu/error-report.h"
>  #include "qapi/error.h"
>  #include "cpu.h"
>  #include "internals.h"
> @@ -509,6 +510,10 @@ static Property arm_cpu_rvbar_property =
>  static Property arm_cpu_has_el3_property =
>              DEFINE_PROP_BOOL("has_el3", ARMCPU, has_el3, true);
>  
> +/* use property name "pmu" to match other archs and virt tools */
> +static Property arm_cpu_has_pmu_property =
> +            DEFINE_PROP_BOOL("pmu", ARMCPU, has_pmu, true);
> +
>  static Property arm_cpu_has_mpu_property =
>              DEFINE_PROP_BOOL("has-mpu", ARMCPU, has_mpu, true);
>  
> @@ -552,6 +557,11 @@ static void arm_cpu_post_init(Object *obj)
>  #endif
>      }
>  
> +    if (arm_feature(&cpu->env, ARM_FEATURE_PMU)) {
> +        qdev_property_add_static(DEVICE(obj), &arm_cpu_has_pmu_property,
> +                                 &error_abort);
> +    }
> +
>      if (arm_feature(&cpu->env, ARM_FEATURE_MPU)) {
>          qdev_property_add_static(DEVICE(obj), &arm_cpu_has_mpu_property,
>                                   &error_abort);
> @@ -648,6 +658,11 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
>          cpu->id_aa64pfr0 &= ~0xf000;
>      }
>  
> +    if (!cpu->has_pmu || !kvm_enabled()) {
> +        cpu->has_pmu = false;
> +        unset_feature(env, ARM_FEATURE_PMU);
> +    }
> +
>      if (!arm_feature(env, ARM_FEATURE_EL2)) {
>          /* Disable the hypervisor feature bits in the processor feature
>           * registers if we don't have EL2. These are id_pfr1[15:12] and
> diff --git a/target-arm/cpu.h b/target-arm/cpu.h
> index 2218c00..b97b93b 100644
> --- a/target-arm/cpu.h
> +++ b/target-arm/cpu.h
> @@ -1129,6 +1129,7 @@ enum arm_features {
>      ARM_FEATURE_V8_SHA256, /* implements SHA256 part of v8 Crypto Extensions */
>      ARM_FEATURE_V8_PMULL, /* implements PMULL part of v8 Crypto Extensions */
>      ARM_FEATURE_THUMB_DSP, /* DSP insns supported in the Thumb encodings */
> +    ARM_FEATURE_PMU, /* has PMU support */
>  };
>  
>  static inline int arm_feature(CPUARMState *env, int feature)
> diff --git a/target-arm/cpu64.c b/target-arm/cpu64.c
> index 1635deb..549cb1e 100644
> --- a/target-arm/cpu64.c
> +++ b/target-arm/cpu64.c
> @@ -111,6 +111,7 @@ static void aarch64_a57_initfn(Object *obj)
>      set_feature(&cpu->env, ARM_FEATURE_V8_PMULL);
>      set_feature(&cpu->env, ARM_FEATURE_CRC);
>      set_feature(&cpu->env, ARM_FEATURE_EL3);
> +    set_feature(&cpu->env, ARM_FEATURE_PMU);
>      cpu->kvm_target = QEMU_KVM_ARM_TARGET_CORTEX_A57;
>      cpu->midr = 0x411fd070;
>      cpu->revidr = 0x00000000;
> @@ -166,6 +167,7 @@ static void aarch64_a53_initfn(Object *obj)
>      set_feature(&cpu->env, ARM_FEATURE_V8_PMULL);
>      set_feature(&cpu->env, ARM_FEATURE_CRC);
>      set_feature(&cpu->env, ARM_FEATURE_EL3);
> +    set_feature(&cpu->env, ARM_FEATURE_PMU);
>      cpu->kvm_target = QEMU_KVM_ARM_TARGET_CORTEX_A53;
>      cpu->midr = 0x410fd034;
>      cpu->revidr = 0x00000000;
> diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c
> index 5faa76c..6111109 100644
> --- a/target-arm/kvm64.c
> +++ b/target-arm/kvm64.c
> @@ -428,6 +428,11 @@ static inline void set_feature(uint64_t *features, int feature)
>      *features |= 1ULL << feature;
>  }
>  
> +static inline void unset_feature(uint64_t *features, int feature)
> +{
> +    *features &= ~(1ULL << feature);
> +}
> +
>  bool kvm_arm_get_host_cpu_features(ARMHostCPUClass *ahcc)
>  {
>      /* Identify the feature bits corresponding to the host CPU, and
> @@ -469,6 +474,7 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUClass *ahcc)
>      set_feature(&features, ARM_FEATURE_VFP4);
>      set_feature(&features, ARM_FEATURE_NEON);
>      set_feature(&features, ARM_FEATURE_AARCH64);
> +    set_feature(&features, ARM_FEATURE_PMU);
>  
>      ahcc->features = features;
>  
> @@ -482,6 +488,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      int ret;
>      uint64_t mpidr;
>      ARMCPU *cpu = ARM_CPU(cs);
> +    CPUARMState *env = &cpu->env;
>  
>      if (cpu->kvm_target == QEMU_KVM_ARM_TARGET_NONE ||
>          !object_dynamic_cast(OBJECT(cpu), TYPE_AARCH64_CPU)) {
> @@ -501,10 +508,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      if (!arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
>          cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_EL1_32BIT;
>      }
> -    if (kvm_irqchip_in_kernel() &&
> -        kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PMU_V3)) {
> -        cpu->has_pmu = true;
> +    if (!kvm_irqchip_in_kernel() ||
> +        !kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PMU_V3)) {
> +            cpu->has_pmu = false;
> +    }
> +    if (cpu->has_pmu) {
>          cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_PMU_V3;
> +    } else {
> +        unset_feature(&env->features, ARM_FEATURE_PMU);
>      }
>  
>      /* Do KVM_ARM_VCPU_INIT ioctl */
> -- 
> 1.8.3.1
> 

[Qemu-devel] [PATCH V8 2/2] arm: virt: add PMU property to mach-virt machine type

[Wei Huang]

CPU vPMU is now turned ON by default, but this feature wasn't introduced
until virt-2.7 machine type. To solve this problem, this patch adds a
PMU option in machine state, which is used to control CPU's vPMU status.
This PMU option is not exposed to command line and is turned off in
virt-2.6 machine type.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Wei Huang <wei@redhat.com>
---
 hw/arm/virt.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 074d11c..e64dc4a 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -85,6 +85,7 @@ typedef struct {
     VirtBoardInfo *daughterboard;
     bool disallow_affinity_adjustment;
     bool no_its;
+    bool no_pmu;
 } VirtMachineClass;
 
 typedef struct {
@@ -1353,6 +1354,10 @@ static void machvirt_init(MachineState *machine)
             }
         }
 
+        if (vmc->no_pmu && object_property_find(cpuobj, "pmu", NULL)) {
+            object_property_set_bool(cpuobj, false, "pmu", NULL);
+        }
+
         if (object_property_find(cpuobj, "reset-cbar", NULL)) {
             object_property_set_int(cpuobj, vbi->memmap[VIRT_CPUPERIPHS].base,
                                     "reset-cbar", &error_abort);
@@ -1588,5 +1593,7 @@ static void virt_machine_2_6_options(MachineClass *mc)
     virt_machine_2_7_options(mc);
     SET_MACHINE_COMPAT(mc, VIRT_COMPAT_2_6);
     vmc->disallow_affinity_adjustment = true;
+    /* Disable PMU for 2.6 as PMU support was first introduced in 2.7 */
+    vmc->no_pmu = true;
 }
 DEFINE_VIRT_MACHINE(2, 6)
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH V8 2/2] arm: virt: add PMU property to mach-virt machine type

[Andrew Jones]

On Wed, Oct 26, 2016 at 02:28:21AM -0400, Wei Huang wrote:
> CPU vPMU is now turned ON by default, but this feature wasn't introduced
> until virt-2.7 machine type. To solve this problem, this patch adds a
> PMU option in machine state, which is used to control CPU's vPMU status.
> This PMU option is not exposed to command line and is turned off in
> virt-2.6 machine type.
> 
> Reviewed-by: Andrew Jones <drjones@redhat.com>
> Signed-off-by: Wei Huang <wei@redhat.com>
> ---
>  hw/arm/virt.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 074d11c..e64dc4a 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -85,6 +85,7 @@ typedef struct {
>      VirtBoardInfo *daughterboard;
>      bool disallow_affinity_adjustment;
>      bool no_its;
> +    bool no_pmu;
>  } VirtMachineClass;
>  
>  typedef struct {
> @@ -1353,6 +1354,10 @@ static void machvirt_init(MachineState *machine)
>              }
>          }
>  
> +        if (vmc->no_pmu && object_property_find(cpuobj, "pmu", NULL)) {
> +            object_property_set_bool(cpuobj, false, "pmu", NULL);
> +        }
> +
>          if (object_property_find(cpuobj, "reset-cbar", NULL)) {
>              object_property_set_int(cpuobj, vbi->memmap[VIRT_CPUPERIPHS].base,
>                                      "reset-cbar", &error_abort);
> @@ -1588,5 +1593,7 @@ static void virt_machine_2_6_options(MachineClass *mc)
>      virt_machine_2_7_options(mc);
>      SET_MACHINE_COMPAT(mc, VIRT_COMPAT_2_6);
>      vmc->disallow_affinity_adjustment = true;
> +    /* Disable PMU for 2.6 as PMU support was first introduced in 2.7 */
> +    vmc->no_pmu = true;
>  }
>  DEFINE_VIRT_MACHINE(2, 6)
> -- 
> 1.8.3.1
> 

Reviewed-by: Andrew Jones <drjones@redhat.com>