[v5] HVF: Add support for platform vGIC and nested virtualisation

[PATCH v5 11/13] hvf: gate ARM_FEATURE_PMU register emulation behind not being at EL2

Posted by Mohamed Mediouni 6 months, 2 weeks ago

From Apple documentation:

> When EL2 is disabled, PMU register accesses trigger "Trapped MSR, MRS, or
> System Instruction" exceptions. When this happens, hv_vcpu_run() returns, and the
>  hv_vcpu_exit_t object contains the information about this exception.

> When EL2 is enabled, the handling of PMU register accesses is determined by the PMUVer
> field of ID_AA64DFR0_EL1 register.
> If the PMUVer field value is zero or is invalid, PMU register accesses generate "Undefined"
> exceptions, which are sent to the guest.
> If the PMUVer field value is non-zero and valid, PMU register accesses are emulated by the framework.
> The ID_AA64DFR0_EL1 register can be modified via hv_vcpu_set_sys_reg API.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 target/arm/hvf/hvf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index a1e928ddfa..f70870fb62 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -1379,7 +1379,7 @@ static int hvf_sysreg_read(CPUState *cpu, uint32_t reg, uint64_t *val)
     ARMCPU *arm_cpu = ARM_CPU(cpu);
     CPUARMState *env = &arm_cpu->env;
 
-    if (arm_feature(env, ARM_FEATURE_PMU)) {
+    if (!hvf_arm_el2_enabled() && arm_feature(env, ARM_FEATURE_PMU)) {
         switch (reg) {
         case SYSREG_PMCR_EL0:
             *val = env->cp15.c9_pmcr;
@@ -1676,7 +1676,7 @@ static int hvf_sysreg_write(CPUState *cpu, uint32_t reg, uint64_t val)
                            SYSREG_OP2(reg),
                            val);
 
-    if (arm_feature(env, ARM_FEATURE_PMU)) {
+    if (!hvf_arm_el2_enabled() && arm_feature(env, ARM_FEATURE_PMU)) {
         switch (reg) {
         case SYSREG_PMCCNTR_EL0:
             pmu_op_start(env);
-- 
2.39.5 (Apple Git-154)

Re: [PATCH v5 11/13] hvf: gate ARM_FEATURE_PMU register emulation behind not being at EL2

Posted by Philippe Mathieu-Daudé 6 months ago

On 28/7/25 15:41, Mohamed Mediouni wrote:
>  From Apple documentation:
> 
>> When EL2 is disabled, PMU register accesses trigger "Trapped MSR, MRS, or
>> System Instruction" exceptions. When this happens, hv_vcpu_run() returns, and the
>>  hv_vcpu_exit_t object contains the information about this exception.
> 
>> When EL2 is enabled, the handling of PMU register accesses is determined by the PMUVer
>> field of ID_AA64DFR0_EL1 register.
>> If the PMUVer field value is zero or is invalid, PMU register accesses generate "Undefined"
>> exceptions, which are sent to the guest.
>> If the PMUVer field value is non-zero and valid, PMU register accesses are emulated by the framework.
>> The ID_AA64DFR0_EL1 register can be modified via hv_vcpu_set_sys_reg API.
> 
> Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
> ---
>   target/arm/hvf/hvf.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>