Re: [PATCH 2/2] KVM: x86 emulator: Drop EFER.SVME requirement from VMMCALL

[Joerg Roedel <joro@8bytes.org>]

On Tue, Apr 05, 2011 at 04:28:31PM +0300, Avi Kivity wrote:
> VMMCALL requires EFER.SVME to be enabled in the host, not in the guest, which
> is what check_svme() checks.

Well, yes and no. The guest has no dedicated EFER. EFER is switched in
VMRUN which is why SVME must be set in the VMCBs EFER. This value makes
it into the arch.efer too with Nested-SVM.
According to the documentation VMMCALL throws an #UD if SVME is 0 which
is why I added the check. On the other hand, at host-level it throws
always an #UD and in the guest EFER.SVME is always enabled, so the check
doesn't really make sense. I just added it because is is documented.

	Joerg

> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kvm/emulate.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index a77c8f6..4aa5d65 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2677,7 +2677,7 @@ static struct opcode group7_rm1[] = {
>  
>  static struct opcode group7_rm3[] = {
>  	DIP(SrcNone | ModRM | Prot | Priv, vmrun,   check_svme_pa),
> -	DIP(SrcNone | ModRM | Prot | VendorSpecific, vmmcall, check_svme),
> +	DI(SrcNone | ModRM | Prot | VendorSpecific, vmmcall),
>  	DIP(SrcNone | ModRM | Prot | Priv, vmload,  check_svme_pa),
>  	DIP(SrcNone | ModRM | Prot | Priv, vmsave,  check_svme_pa),
>  	DIP(SrcNone | ModRM | Prot | Priv, stgi,    check_svme),
> -- 
> 1.7.1
> 
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