Re: [Xen-devel] [PATCH v3 1/8] x86/vmx_update_guest_cr: minor optimization

[Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>]

On 7/6/2016 6:49 PM, Corneliu ZUZU wrote:
> Minor optimization @ vmx_update_guest_cr: checks if v->arch.hvm_vmx.exec_control
> was modified before actually calling vmx_update_cpu_exec_control(v).
>
> Signed-off-by: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>
> ---
> Changed since v2: <nothing>
> ---
>   xen/arch/x86/hvm/vmx/vmx.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index df19579..8ab074f 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -1434,8 +1434,10 @@ static void vmx_update_guest_cr(struct vcpu *v, unsigned 
> int cr)
>           if ( paging_mode_hap(v->domain) )
>           {
>               /* Manage GUEST_CR3 when CR0.PE=0. */
> +            uint32_t old_ctls = v->arch.hvm_vmx.exec_control;
>               uint32_t cr3_ctls = (CPU_BASED_CR3_LOAD_EXITING |
>                                    CPU_BASED_CR3_STORE_EXITING);
> +
>               v->arch.hvm_vmx.exec_control &= ~cr3_ctls;
>               if ( !hvm_paging_enabled(v) && !vmx_unrestricted_guest(v) )
>                   v->arch.hvm_vmx.exec_control |= cr3_ctls;
> @@ -1445,7 +1447,8 @@ static void vmx_update_guest_cr(struct vcpu *v, unsigned 
> int cr)
>                    monitor_ctrlreg_bitmask(VM_EVENT_X86_CR3) )
>                   v->arch.hvm_vmx.exec_control |= CPU_BASED_CR3_LOAD_EXITING;
>   
> -            vmx_update_cpu_exec_control(v);
> +            if ( old_ctls != v->arch.hvm_vmx.exec_control )
> +                vmx_update_cpu_exec_control(v);
>           }
>   
>           if ( !nestedhvm_vcpu_in_guestmode(v) )
Jan,

I'm wondering if you could ack this as well (if there's nothing wrong w/ 
it) and push it to be done with it. :-)
Thanks,
Corneliu.

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