Re: [PATCH 05/10] KVM: nVMX: Allocate shadow vmcs

[Gleb Natapov <gleb@redhat.com>]

On Wed, Apr 17, 2013 at 02:53:10PM +0300, Abel Gordon wrote:
> Allocate a shadow vmcs used by the processor to shadow part of the fields
> stored in the software defined VMCS12 (let L1 access fields without causing
> exits). Note we keep a shadow vmcs only for the current vmcs12.  Once a vmcs12
> becomes non-current, its shadow vmcs is released.
> 
> 
> Signed-off-by: Abel Gordon <abelg@il.ibm.com>
> ---
>  arch/x86/kvm/vmx.c |   15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> --- .before/arch/x86/kvm/vmx.c	2013-04-17 14:20:50.000000000 +0300
> +++ .after/arch/x86/kvm/vmx.c	2013-04-17 14:20:50.000000000 +0300
> @@ -355,6 +355,7 @@ struct nested_vmx {
>  	/* The host-usable pointer to the above */
>  	struct page *current_vmcs12_page;
>  	struct vmcs12 *current_vmcs12;
> +	struct vmcs *current_shadow_vmcs;
>  
>  	/* vmcs02_list cache of VMCSs recently used to run L2 guests */
>  	struct list_head vmcs02_pool;
> @@ -5980,6 +5981,7 @@ static int handle_vmptrld(struct kvm_vcp
>  	gva_t gva;
>  	gpa_t vmptr;
>  	struct x86_exception e;
> +	struct vmcs *shadow_vmcs;
>  
>  	if (!nested_vmx_check_permission(vcpu))
>  		return 1;
> @@ -6026,6 +6028,19 @@ static int handle_vmptrld(struct kvm_vcp
>  		vmx->nested.current_vmptr = vmptr;
>  		vmx->nested.current_vmcs12 = new_vmcs12;
>  		vmx->nested.current_vmcs12_page = page;
> +		if (enable_shadow_vmcs) {
> +			shadow_vmcs = alloc_vmcs();
Next patch frees vmx->nested.current_shadow_vmcs couple of lines above.
What about reusing previous page instead of allocation new one each
time?

> +			if (!shadow_vmcs) {
> +				nested_vmx_failInvalid(vcpu);
> +				skip_emulated_instruction(vcpu);
> +				return 1;
> +			}
> +			/* mark vmcs as shadow */
> +			shadow_vmcs->revision_id |= (1u << 31);
> +			/* init shadow vmcs */
> +			vmcs_clear(shadow_vmcs);
> +			vmx->nested.current_shadow_vmcs = shadow_vmcs;
> +		}
>  	}
>  
>  	nested_vmx_succeed(vcpu);
> 
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

--
			Gleb.