[Qemu-devel] Re: [PATCH 1/4] kvm: Add support for querying supported cpu features

[Anthony Liguori <aliguori@us.ibm.com>]

Avi Kivity wrote:
> kvm does not support all cpu features; add support for dunamically querying
> the supported feature set.
>
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  kvm.h             |    3 ++
>  target-i386/kvm.c |   80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 83 insertions(+), 0 deletions(-)
>
> diff --git a/kvm.h b/kvm.h
> index bd4e8d4..c134c45 100644
> --- a/kvm.h
> +++ b/kvm.h
> @@ -124,6 +124,9 @@ void kvm_arch_remove_all_hw_breakpoints(void);
>  
>  void kvm_arch_update_guest_debug(CPUState *env, struct kvm_guest_debug *dbg);
>  
> +uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function,
> +                                      int reg);
> +
>  /* generic hooks - to be moved/refactored once there are more users */
>  
>  static inline void cpu_synchronize_state(CPUState *env, int modified)
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index b534b2d..5f54ff5 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -34,6 +34,86 @@
>      do { } while (0)
>  #endif
>  
> +#ifdef KVM_CAP_EXT_CPUID
> +
> +static struct kvm_cpuid2 *try_get_cpuid(KVMState *s, int max)
> +{
> +    struct kvm_cpuid2 *cpuid;
> +    int r, size;
> +
> +    size = sizeof(*cpuid) + max * sizeof(*cpuid->entries);
> +    cpuid = (struct kvm_cpuid2 *)qemu_mallocz(size);
> +    cpuid->nent = max;
> +    r = kvm_ioctl(s, KVM_GET_SUPPORTED_CPUID, cpuid);
> +    if (r < 0) {
> +        if (r == -E2BIG) {
> +            qemu_free(cpuid);
> +            return NULL;
> +        } else {
> +            fprintf(stderr, "KVM_GET_SUPPORTED_CPUID failed: %s\n",
> +                    strerror(-r));
> +            exit(1);
> +        }
> +    }
> +    return cpuid;
> +}
> +
> +uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function, int reg)
> +{
> +    struct kvm_cpuid2 *cpuid;
> +    int i, max;
> +    uint32_t ret = 0;
> +    uint32_t cpuid_1_edx;
> +
> +    if (!kvm_check_extension(KVM_CAP_EXT_CPUID)) {
> +        return -1U;
> +    

kvm_check_extension doesn't exist in upstream QEMU.  It's a good idea 
though so I added it in a previous commit.  However, I changed the 
signature to it to take a KVMState * as the first argument (which is 
available in env->kvm_state).  I updated this patch to pass the extra 
's' parameter.

Regards,

Anthony Liguori


-- 
Regards,

Anthony Liguori