Re: [Qemu-devel] [PATCH v2 01/14] target/arm/cpu64: Ensure kvm really supports aarch64=off

[Auger Eric <eric.auger@redhat.com>]

Hi Drew,

On 7/24/19 3:52 PM, Andrew Jones wrote:
> On Wed, Jul 24, 2019 at 02:51:15PM +0200, Auger Eric wrote:
>> Hi Drew,
>>
>> On 6/25/19 3:34 PM, Andrew Jones wrote:
>>> On Tue, Jun 25, 2019 at 11:35:12AM +0200, Auger Eric wrote:
>>>> Hi Drew,
>>>>
>>>> On 6/21/19 6:34 PM, Andrew Jones wrote:
>>>>> If -cpu <cpu>,aarch64=off is used then KVM must also be used, and it
>>>>> and the host must support running the vcpu in 32-bit mode. Also, if
>> s/and it//
> 
> "and it and the host" means "and KVM and the host", as 'it' refers to the
> last subject, which is KVM. I wanted to point out both the host (machine)
> and KVM (version of kernel with KVM) need to support the feature.
hum ok
> 
>>>>> -cpu <cpu>,aarch64=on is used, then it doesn't matter if kvm is
>>>>> enabled or not.
>>>>>
>>>>> Signed-off-by: Andrew Jones <drjones@redhat.com>
>>>>
>>>>
>>>>> ---
>>>>>  target/arm/cpu64.c   | 12 ++++++------
>>>>>  target/arm/kvm64.c   | 11 +++++++++++
>>>>>  target/arm/kvm_arm.h | 14 ++++++++++++++
>>>>>  3 files changed, 31 insertions(+), 6 deletions(-)
>>>>>
>>>>> diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
>>>>> index 1901997a0645..946994838d8a 100644
>>>>> --- a/target/arm/cpu64.c
>>>>> +++ b/target/arm/cpu64.c
>>>>> @@ -407,13 +407,13 @@ static void aarch64_cpu_set_aarch64(Object *obj, bool value, Error **errp)
>>>>>       * restriction allows us to avoid fixing up functionality that assumes a
>>>>>       * uniform execution state like do_interrupt.
>>>>>       */> -    if (!kvm_enabled()) {
>>>>> -        error_setg(errp, "'aarch64' feature cannot be disabled "
>>>>> -                         "unless KVM is enabled");
>>>>> -        return;
>>>>> -    }
>>>>> -
>>>>>      if (value == false) {
>>>>> +        if (!kvm_enabled() || !kvm_arm_aarch32_supported(CPU(cpu))) {
>>>>> +            error_setg(errp, "'aarch64' feature cannot be disabled "
>>>>> +                             "unless KVM is enabled and 32-bit EL1 "
>>>>> +                             "is supported");
>>>>> +            return;
>>>>> +        }
>>>>>          unset_feature(&cpu->env, ARM_FEATURE_AARCH64);
>>>>>      } else {
>>>>>          set_feature(&cpu->env, ARM_FEATURE_AARCH64);
>>>>> diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
>>>>> index 22d19c9aec6f..45ccda589903 100644
>>>>> --- a/target/arm/kvm64.c
>>>>> +++ b/target/arm/kvm64.c
>>>>> @@ -24,7 +24,9 @@
>>>>>  #include "exec/gdbstub.h"
>>>>>  #include "sysemu/sysemu.h"
>>>>>  #include "sysemu/kvm.h"
>>>>> +#include "sysemu/kvm_int.h"
>>>>>  #include "kvm_arm.h"
>>>>> +#include "hw/boards.h"
>> By the way those two new headers are not needed by this patch
> 
> Really?
> 
> current_machine is defined in hw/boards.h and KVM_STATE is defined
> in sysemu/kvm_int.h.
argh my bad.

Sorry for the noise

Eric
> 
>>>>>  #include "internals.h"
>>>>>  
>>>>>  static bool have_guest_debug;
>>>>> @@ -593,6 +595,15 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>>>>>      return true;
>>>>>  }
>>>>>  
>>>>> +bool kvm_arm_aarch32_supported(CPUState *cpu)
>>>>> +{
>>>>> +    KVMState *s = KVM_STATE(current_machine->accelerator);
>>>>> +    int ret;
>>>>> +
>>>>> +    ret = kvm_check_extension(s, KVM_CAP_ARM_EL1_32BIT);
>>>>> +    return ret > 0;
>>>> nit: return kvm_check_extension() should be sufficient
>>>
>>> Ah yes, I forgot kvm_check_extension() already converts negative
>>> error codes to zero. I'll fix that for v3.
>>>
>>>>> +}
>>>>> +
>>>>>  #define ARM_CPU_ID_MPIDR       3, 0, 0, 0, 5
>>>>>  
>>>>>  int kvm_arch_init_vcpu(CPUState *cs)
>>>>> diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
>>>>> index 2a07333c615f..812125f805a1 100644
>>>>> --- a/target/arm/kvm_arm.h
>>>>> +++ b/target/arm/kvm_arm.h
>>>>> @@ -207,6 +207,15 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf);
>>>>>   */
>>>>>  void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu);
>>>>>  
>>>>> +/**
>>>>> + * kvm_arm_aarch32_supported:
>>>>> + * @cs: CPUState
>>>> use kernel-doc comment style?
>>>
>>> This file (kvm_arm.h) doesn't appear to have a super consistent comment
>>> style. I see some use @var: for the parameters and some have 'Returns:
>>> ...' lines as well. I'm happy to do whatever the maintainers prefer. For
>>> now I was just trying to mimic whatever caught my eye.>
>>>>> + *
>>>>> + * Returns true if the KVM VCPU can enable AArch32 mode and false
>>>>> + * otherwise.
>>>>> + */
>>>>> +bool kvm_arm_aarch32_supported(CPUState *cs);
>>>>> +
>>>>>  /**
>>>>>   * kvm_arm_get_max_vm_ipa_size - Returns the number of bits in the
>>>>>   * IPA address space supported by KVM
>>>>> @@ -247,6 +256,11 @@ static inline void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
>>>>>      cpu->host_cpu_probe_failed = true;
>>>>>  }
>>>>>  
>>>>> +static inline bool kvm_arm_aarch32_supported(CPUState *cs)
>>>>> +{
>>>>> +    return false;
>>>>> +}
>>>>> +
>>>>>  static inline int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
>>>>>  {
>>>>>      return -ENOENT;
>>>>>
>>>> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> 
> Thanks,
> drew
>