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

[Andrew Jones]

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
> > -cpu <cpu>,aarch64=on is used, then it doesn't matter if kvm is
> > enabled or not.
> > 
> > Signed-off-by: Andrew Jones <address@hidden>
> 
> 
> > ---
> >  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"
> >  #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 <address@hidden>
>

Thanks,
drew