Re: [Xen-devel] [PATCH 13/13] xen/arm: Avoid to use current everywhere in enter_hypervisor_head

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 22 May 2018, Julien Grall wrote:
> Using current is fairly expensive, so save up into a variable.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Good idea. I am curious to know actually how much this patch would save
but I am not going to ask you run the tests.

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

> ---
>  xen/arch/arm/traps.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 020b0b8eef..b1546f6907 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -2024,8 +2024,10 @@ static void enter_hypervisor_head(struct cpu_user_regs 
> *regs)
>  {
>      if ( guest_mode(regs) )
>      {
> +        struct vcpu *v = current;
> +
>          /* If the guest has disabled the workaround, bring it back on. */
> -        if ( needs_ssbd_flip(current) )
> +        if ( needs_ssbd_flip(v) )
>              arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_2_FID, 1, NULL);
>  
>          /*
> @@ -2034,8 +2036,8 @@ static void enter_hypervisor_head(struct cpu_user_regs 
> *regs)
>           * but the crucial bit is "On taking a vSError interrupt, HCR_EL2.VSE
>           * (alias of HCR.VA) is cleared to 0."
>           */
> -        if ( current->arch.hcr_el2 & HCR_VA )
> -            current->arch.hcr_el2 = READ_SYSREG(HCR_EL2);
> +        if ( v->arch.hcr_el2 & HCR_VA )
> +            v->arch.hcr_el2 = READ_SYSREG(HCR_EL2);
>  
>  #ifdef CONFIG_NEW_VGIC
>          /*
> @@ -2045,11 +2047,11 @@ static void enter_hypervisor_head(struct 
> cpu_user_regs *regs)
>           * TODO: Investigate whether this is necessary to do on every
>           * trap and how it can be optimised.
>           */
> -        vtimer_update_irqs(current);
> -        vcpu_update_evtchn_irq(current);
> +        vtimer_update_irqs(v);
> +        vcpu_update_evtchn_irq(v);
>  #endif
>  
> -        vgic_sync_from_lrs(current);
> +        vgic_sync_from_lrs(v);
>      }
>  }
>  
> -- 
> 2.11.0
> 

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