Re: [PATCH v2 01/11] KVM: nSVM: don't sync back tlb_ctl on nested VM exit

[Santosh Shukla]

Hi Maxim,

On 11/30/2022 1:07 AM, Maxim Levitsky wrote:
> The CPU doesn't change TLB_CTL value as stated in the PRM (15.16.2):
> 
nits:
s / PRM (15.16.2) / APM (15.16.1 - TLB Flush)

>   "The VMRUN instruction reads, but does not change, the
>   value of the TLB_CONTROL field"
> 
> Therefore the KVM shouldn't do that either.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> ---
>  arch/x86/kvm/svm/nested.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index bc9cd7086fa972..37af0338da7c32 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1010,7 +1010,6 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
>  		vmcb12->control.next_rip  = vmcb02->control.next_rip;
>  
>  	vmcb12->control.int_ctl           = svm->nested.ctl.int_ctl;
> -	vmcb12->control.tlb_ctl           = svm->nested.ctl.tlb_ctl;
>  	vmcb12->control.event_inj         = svm->nested.ctl.event_inj;
>  	vmcb12->control.event_inj_err     = svm->nested.ctl.event_inj_err;
>