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[PATCH v7 3/4] target/arm: Enable feature ARM_FEATURE_EL2 if EL2 is supported

Eric Auger posted 4 patches 4 months, 2 weeks ago
Maintainers: Peter Maydell <peter.maydell@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>
There is a newer version of this series
[PATCH v7 3/4] target/arm: Enable feature ARM_FEATURE_EL2 if EL2 is supported
Posted by Eric Auger 4 months, 2 weeks ago 
From: Haibo Xu <haibo.xu@linaro.org>

KVM_CAP_ARM_EL2 must be supported by the cpu to enable ARM_FEATURE_EL2.
In case the host does support NV, expose the feature.

Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

---
v2 -> v3:
- check pmu->has_el2 on kvm_arch_init_vcpu() when setting
  KVM_ARM_VCPU_HAS_EL2 feature (Peter)

v1 -> v2:
- remove isar_feature_aa64_aa32_el2 modif in target/arm/cpu.h
  [Richard] and use el2_supported in kvm_arch_init_vcpu
---
 target/arm/kvm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index e5708e54ae..46e5f19637 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -250,6 +250,7 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
      */
     int fdarray[3];
     bool sve_supported;
+    bool el2_supported;
     bool pmu_supported = false;
     uint64_t features = 0;
     int err;
@@ -269,6 +270,14 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         init.features[0] |= 1 << KVM_ARM_VCPU_SVE;
     }
 
+    /*
+     * Ask for EL2 if supported.
+     */
+    el2_supported = kvm_arm_el2_supported();
+    if (el2_supported) {
+        init.features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
+    }
+
     /*
      * Ask for Pointer Authentication if supported, so that we get
      * the unsanitized field values for AA64ISAR1_EL1.
@@ -422,6 +431,10 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
     features |= 1ULL << ARM_FEATURE_AARCH64;
     features |= 1ULL << ARM_FEATURE_GENERIC_TIMER;
 
+    if (el2_supported) {
+        features |= 1ULL << ARM_FEATURE_EL2;
+    }
+
     ahcf->features = features;
 
     return true;
@@ -1887,6 +1900,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
         cpu->kvm_init_features[0] |= (1 << KVM_ARM_VCPU_PTRAUTH_ADDRESS |
                                       1 << KVM_ARM_VCPU_PTRAUTH_GENERIC);
     }
+    if (cpu->has_el2 && kvm_arm_el2_supported()) {
+        cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
+    }
 
     /* Do KVM_ARM_VCPU_INIT ioctl */
     ret = kvm_arm_vcpu_init(cpu);
-- 
2.49.0
Re: [PATCH v7 3/4] target/arm: Enable feature ARM_FEATURE_EL2 if EL2 is supported
Posted by Peter Maydell 4 months, 2 weeks ago 
On Wed, 2 Jul 2025 at 17:31, Eric Auger <eric.auger@redhat.com> wrote:
>
> From: Haibo Xu <haibo.xu@linaro.org>
>
> KVM_CAP_ARM_EL2 must be supported by the cpu to enable ARM_FEATURE_EL2.
> In case the host does support NV, expose the feature.
>
> Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
> Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>
> ---
> v2 -> v3:
> - check pmu->has_el2 on kvm_arch_init_vcpu() when setting
>   KVM_ARM_VCPU_HAS_EL2 feature (Peter)
>
> v1 -> v2:
> - remove isar_feature_aa64_aa32_el2 modif in target/arm/cpu.h
>   [Richard] and use el2_supported in kvm_arch_init_vcpu
> ---
>  target/arm/kvm.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index e5708e54ae..46e5f19637 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -250,6 +250,7 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>       */
>      int fdarray[3];
>      bool sve_supported;
> +    bool el2_supported;
>      bool pmu_supported = false;
>      uint64_t features = 0;
>      int err;
> @@ -269,6 +270,14 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>          init.features[0] |= 1 << KVM_ARM_VCPU_SVE;
>      }
>
> +    /*
> +     * Ask for EL2 if supported.
> +     */
> +    el2_supported = kvm_arm_el2_supported();
> +    if (el2_supported) {
> +        init.features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
> +    }
> +
>      /*
>       * Ask for Pointer Authentication if supported, so that we get
>       * the unsanitized field values for AA64ISAR1_EL1.
> @@ -422,6 +431,10 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>      features |= 1ULL << ARM_FEATURE_AARCH64;
>      features |= 1ULL << ARM_FEATURE_GENERIC_TIMER;
>
> +    if (el2_supported) {
> +        features |= 1ULL << ARM_FEATURE_EL2;
> +    }
> +
>      ahcf->features = features;
>
>      return true;
> @@ -1887,6 +1900,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
>          cpu->kvm_init_features[0] |= (1 << KVM_ARM_VCPU_PTRAUTH_ADDRESS |
>                                        1 << KVM_ARM_VCPU_PTRAUTH_GENERIC);
>      }
> +    if (cpu->has_el2 && kvm_arm_el2_supported()) {
> +        cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
> +    }
>
>      /* Do KVM_ARM_VCPU_INIT ioctl */
>      ret = kvm_arm_vcpu_init(cpu);
> --

How does this interact with creating an aarch32 VM with
"-cpu host,aarch64=off" ?  Looking at the kernel, it will
fail vcpu_init if you ask for a vcpu with both EL1_32BIT
and HAS_EL2. I guess since the virt board will only request
HAS_EL2 if you say virtualization=on this is fine. Do we
give a sensible error message if the user tries
 -accel kvm -M virt,virtualization=on -cpu host,aarch64=off   ?

-- PMM
Re: [PATCH v7 3/4] target/arm: Enable feature ARM_FEATURE_EL2 if EL2 is supported
Posted by Eric Auger 4 months, 1 week ago 
Hi Peter,

On 7/4/25 2:14 PM, Peter Maydell wrote:
> On Wed, 2 Jul 2025 at 17:31, Eric Auger <eric.auger@redhat.com> wrote:
>> From: Haibo Xu <haibo.xu@linaro.org>
>>
>> KVM_CAP_ARM_EL2 must be supported by the cpu to enable ARM_FEATURE_EL2.
>> In case the host does support NV, expose the feature.
>>
>> Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
>> Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>>
>> ---
>> v2 -> v3:
>> - check pmu->has_el2 on kvm_arch_init_vcpu() when setting
>>   KVM_ARM_VCPU_HAS_EL2 feature (Peter)
>>
>> v1 -> v2:
>> - remove isar_feature_aa64_aa32_el2 modif in target/arm/cpu.h
>>   [Richard] and use el2_supported in kvm_arch_init_vcpu
>> ---
>>  target/arm/kvm.c | 16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
>>
>> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
>> index e5708e54ae..46e5f19637 100644
>> --- a/target/arm/kvm.c
>> +++ b/target/arm/kvm.c
>> @@ -250,6 +250,7 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>>       */
>>      int fdarray[3];
>>      bool sve_supported;
>> +    bool el2_supported;
>>      bool pmu_supported = false;
>>      uint64_t features = 0;
>>      int err;
>> @@ -269,6 +270,14 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>>          init.features[0] |= 1 << KVM_ARM_VCPU_SVE;
>>      }
>>
>> +    /*
>> +     * Ask for EL2 if supported.
>> +     */
>> +    el2_supported = kvm_arm_el2_supported();
>> +    if (el2_supported) {
>> +        init.features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
>> +    }
>> +
>>      /*
>>       * Ask for Pointer Authentication if supported, so that we get
>>       * the unsanitized field values for AA64ISAR1_EL1.
>> @@ -422,6 +431,10 @@ static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>>      features |= 1ULL << ARM_FEATURE_AARCH64;
>>      features |= 1ULL << ARM_FEATURE_GENERIC_TIMER;
>>
>> +    if (el2_supported) {
>> +        features |= 1ULL << ARM_FEATURE_EL2;
>> +    }
>> +
>>      ahcf->features = features;
>>
>>      return true;
>> @@ -1887,6 +1900,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
>>          cpu->kvm_init_features[0] |= (1 << KVM_ARM_VCPU_PTRAUTH_ADDRESS |
>>                                        1 << KVM_ARM_VCPU_PTRAUTH_GENERIC);
>>      }
>> +    if (cpu->has_el2 && kvm_arm_el2_supported()) {
>> +        cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
>> +    }
>>
>>      /* Do KVM_ARM_VCPU_INIT ioctl */
>>      ret = kvm_arm_vcpu_init(cpu);
>> --
> How does this interact with creating an aarch32 VM with
> "-cpu host,aarch64=off" ?  Looking at the kernel, it will
> fail vcpu_init if you ask for a vcpu with both EL1_32BIT
> and HAS_EL2. I guess since the virt board will only request
> HAS_EL2 if you say virtualization=on this is fine. Do we
> give a sensible error message if the user tries
>  -accel kvm -M virt,virtualization=on -cpu host,aarch64=off   ?
Not yet. I will add one.

Thanks!

Eric
>
> -- PMM
>

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