Re: [Qemu-devel] [PATCH v6 07/18] kvm: add kvm_arm_get_max_vm_phys_shift

[Peter Maydell <peter.maydell@linaro.org>]

On Tue, 5 Feb 2019 at 17:33, Eric Auger <eric.auger@redhat.com> wrote:
>
> Add the kvm_arm_get_max_vm_phys_shift() helper that returns the
> log of the maximum IPA size supported by KVM. This capability
> needs to be known to create the VM with a specific IPA max size
> (kvm_type passed along KVM_CREATE_VM ioctl.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
> v4 -> v5:
> - return 40 if the host does not support the capability
>
> v3 -> v4:
> - s/s/ms in kvm_arm_get_max_vm_phys_shift function comment
> - check KVM_CAP_ARM_VM_IPA_SIZE extension
>
> v1 -> v2:
> - put this in ARM specific code
> ---
>  target/arm/kvm.c     | 10 ++++++++++
>  target/arm/kvm_arm.h | 13 +++++++++++++
>  2 files changed, 23 insertions(+)
>
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index e00ccf9c98..fc1dd3ec6a 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -18,6 +18,7 @@
>  #include "qemu/error-report.h"
>  #include "sysemu/sysemu.h"
>  #include "sysemu/kvm.h"
> +#include "sysemu/kvm_int.h"
>  #include "kvm_arm.h"
>  #include "cpu.h"
>  #include "trace.h"
> @@ -162,6 +163,15 @@ void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
>      env->features = arm_host_cpu_features.features;
>  }
>
> +int kvm_arm_get_max_vm_phys_shift(MachineState *ms)
> +{
> +    KVMState *s = KVM_STATE(ms->accelerator);
> +    int ret;
> +
> +    ret = kvm_check_extension(s, KVM_CAP_ARM_VM_IPA_SIZE);

Why not name the function the same as the extension name?

> +    return ret > 0 ? ret : 40;
> +}
> +
>  int kvm_arch_init(MachineState *ms, KVMState *s)
>  {
>      /* For ARM interrupt delivery is always asynchronous,
> diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
> index 6393455b1d..0728bbfa6b 100644
> --- a/target/arm/kvm_arm.h
> +++ b/target/arm/kvm_arm.h
> @@ -207,6 +207,14 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf);
>   */
>  void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu);
>
> +/**
> + * kvm_arm_get_max_vm_phys_shift - Returns log2 of the max IPA size
> + * supported by KVM

This is the number of bits in the IPA address space,
right (ie 40 for a 40-bit IPA, and so on) ? If so, then
I think "Return number of bits in the IPA address space"
might be clearer.

> + *
> + * @ms: Machine state handle
> + */
> +int kvm_arm_get_max_vm_phys_shift(MachineState *ms);

thanks
-- PMM