Re: [Xen-devel] [PATCH v2 3/3] x86/hvm: check HAP before enabling nested VMX

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.02.17 at 10:41, <haozhong.zhang@xxxxxxxxx> wrote:
> The current implementation of nested VMX cannot work without HAP.

Of course the better route would be to fix the actual problem,
the more that - according to other feedback you've got elsewhere -
this apparently is a regression. Nevertheless I can see you perhaps
not having the time to do so, so as a band aid it's likely fine.
However ...

> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4123,7 +4123,7 @@ static int hvmop_set_param(
>           * Remove the check below once we have
>           * shadow-on-shadow.
>           */
> -        if ( cpu_has_svm && !paging_mode_hap(d) && a.value )
> +        if ( (cpu_has_svm || cpu_has_vmx) && !paging_mode_hap(d) && a.value )

... you want to simply drop the cpu_has_svm check here instead of
adding to it, as with neither SVM nor VMX available execution will
never come here.

Jan


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