Re: [PATCH] KVM: Fix MAXPHYADDR calculation when cpuid does not support it

[Pekka Enberg <penberg@cs.helsinki.fi>]

Avi Kivity wrote:
> MAXPHYADDR is derived from cpuid 0x80000008, but when that isn't present, we
> get some random value.
> 
> Fix by checking first that cpuid 0x80000008 is supported.
> 
> Pekka Enberg <penberg@cs.helsinki.fi>
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kvm/x86.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fd5c3d3..b2460cd 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4165,9 +4165,13 @@ int cpuid_maxphyaddr(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpuid_entry2 *best;
>  
> +	best = kvm_find_cpuid_entry(vcpu, 0x80000000, 0);
> +	if (!best || best->eax < 0x80000008)
> +		goto not_found;
>  	best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
>  	if (best)
>  		return best->eax & 0xff;
> +not_found:
>  	return 36;
>  }
>  

Hmm, doesn't seem to work here. I still that triple fault in guest.