Re: [RFC v1 08/25] target/arm/kvm: Use kvm_vm_check_extension() where necessary

On Mon, Jul 13, 2026 at 10:43:37AM +1000, Gavin Shan wrote:
> On 7/8/26 8:42 AM, Mathieu Poirier wrote:
> > From: Jean-Philippe Brucker <[email protected]>
> > 
> > The Arm KVM code can return different values from KVM_CHECK_EXTENSION
> > depending on the VM type. Use kvm_vm_check_extension() where necessary
> > to ensure we get the right response from KVM.
> > 
> > Signed-off-by: Jean-Philippe Brucker <[email protected]>
> > Signed-off-by: Mathieu Poirier <[email protected]>
> > ---
> >   target/arm/kvm.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> 
> I'm putting a note here so that we won't forget. The following changes are needed
> so that capability KVM_CAP_ARM_NISV_TO_USER won't be enabled for realm guest since
> it has been hidden from the realm guest in (v14) host series.
> 
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index 3d5e16a21c..4c52ee7e1b 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -623,7 +623,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>          return -EINVAL;
>      }
> -    if (kvm_check_extension(s, KVM_CAP_ARM_NISV_TO_USER)) {
> +    if (kvm_vm_check_extension(s, KVM_CAP_ARM_NISV_TO_USER)) {

Addressed.

>          if (kvm_vm_enable_cap(s, KVM_CAP_ARM_NISV_TO_USER, 0)) {
>              error_report("Failed to enable KVM_CAP_ARM_NISV_TO_USER cap");
>          } else {
> 
> > diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> > index 6aa1cd04e484..c69b5310c184 100644
> > --- a/target/arm/kvm.c
> > +++ b/target/arm/kvm.c
> > @@ -328,7 +328,7 @@ static void kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
> >                                1 << KVM_ARM_VCPU_PTRAUTH_GENERIC);
> >       }
> > -    if (kvm_check_extension(kvm_state, KVM_CAP_ARM_PMU_V3)) {
> > +    if (kvm_vm_check_extension(kvm_state, KVM_CAP_ARM_PMU_V3)) {
> >           init.features[0] |= 1 << KVM_ARM_VCPU_PMU_V3;
> >           pmu_supported = true;
> >           features |= 1ULL << ARM_FEATURE_PMU;
> > @@ -654,11 +654,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
> >           }
> >       }
> > -    max_hw_wps = kvm_check_extension(s, KVM_CAP_GUEST_DEBUG_HW_WPS);
> > +    max_hw_wps = kvm_vm_check_extension(s, KVM_CAP_GUEST_DEBUG_HW_WPS);
> >       hw_watchpoints = g_array_sized_new(true, true,
> >                                          sizeof(HWWatchpoint), max_hw_wps);
> > -    max_hw_bps = kvm_check_extension(s, KVM_CAP_GUEST_DEBUG_HW_BPS);
> > +    max_hw_bps = kvm_vm_check_extension(s, KVM_CAP_GUEST_DEBUG_HW_BPS);
> >       hw_breakpoints = g_array_sized_new(true, true,
> >                                          sizeof(HWBreakpoint), max_hw_bps);
> > @@ -1905,7 +1905,7 @@ void kvm_arm_pvtime_init(ARMCPU *cpu, uint64_t ipa)
> >   void kvm_arm_steal_time_finalize(ARMCPU *cpu, Error **errp)
> >   {
> > -    bool has_steal_time = kvm_check_extension(kvm_state, KVM_CAP_STEAL_TIME);
> > +    bool has_steal_time = kvm_vm_check_extension(kvm_state, KVM_CAP_STEAL_TIME);
> >       if (cpu->kvm_steal_time == ON_OFF_AUTO_AUTO) {
> >           if (!has_steal_time || !arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
>