Re: [PATCH] always report x2apic as supported feature

[Marcelo Tosatti <mtosatti@redhat.com>]

On Sun, Jul 12, 2009 at 04:10:55PM +0300, Gleb Natapov wrote:
> We emulate x2apic in software, so host support is not required.
> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 00844eb..c256da7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1497,6 +1497,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  	case 1:
>  		entry->edx &= kvm_supported_word0_x86_features;
>  		entry->ecx &= kvm_supported_word4_x86_features;
> +		/* we support x2apic emulation even if host does not support
> +		   it since we emulate x2apic in software */
> +		entry->ecx |= F(X2APIC);
>  		break;
>  	/* function 2 entries are STATEFUL. That is, repeated cpuid commands
>  	 * may return different values. This forces us to get_cpu() before
> --
> 			Gleb.

What if you have an older host that does not support emulate x2apic?