linux-kernel - Re: [PATCH v3 2/9] context_tracking: Move guest exit vtime accounting to separate helpers

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Date:   Tue, 20 Apr 2021 20:48:22 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Michael Tokarev <mjt@....msk.ru>
Subject: Re: [PATCH v3 2/9] context_tracking: Move guest exit vtime accounting
 to separate helpers



On 16.04.21 00:20, Sean Christopherson wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
> 
> Provide separate vtime accounting functions for guest exit instead of
> open coding the logic within the context tracking code.  This will allow
> KVM x86 to handle vtime accounting slightly differently when using
> tick-based accounting.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Michael Tokarev <mjt@....msk.ru>
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> Co-developed-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>

> ---
>   include/linux/context_tracking.h | 24 +++++++++++++++++-------
>   1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
> index 200d30cb3a82..7cf03a8e5708 100644
> --- a/include/linux/context_tracking.h
> +++ b/include/linux/context_tracking.h
> @@ -137,15 +137,20 @@ static __always_inline void context_tracking_guest_exit_irqoff(void)
>   		__context_tracking_exit(CONTEXT_GUEST);
>   }
>   
> -static __always_inline void guest_exit_irqoff(void)
> +static __always_inline void vtime_account_guest_exit(void)
>   {
> -	context_tracking_guest_exit_irqoff();
> -
> -	instrumentation_begin();
>   	if (vtime_accounting_enabled_this_cpu())
>   		vtime_guest_exit(current);
>   	else
>   		current->flags &= ~PF_VCPU;
> +}
> +
> +static __always_inline void guest_exit_irqoff(void)
> +{
> +	context_tracking_guest_exit_irqoff();
> +
> +	instrumentation_begin();
> +	vtime_account_guest_exit();
>   	instrumentation_end();
>   }
>   
> @@ -166,12 +171,17 @@ static __always_inline void guest_enter_irqoff(void)
>   
>   static __always_inline void context_tracking_guest_exit_irqoff(void) { }
>   
> -static __always_inline void guest_exit_irqoff(void)
> +static __always_inline void vtime_account_guest_exit(void)
>   {
> -	instrumentation_begin();
> -	/* Flush the guest cputime we spent on the guest */
>   	vtime_account_kernel(current);
>   	current->flags &= ~PF_VCPU;
> +}
> +
> +static __always_inline void guest_exit_irqoff(void)
> +{
> +	instrumentation_begin();
> +	/* Flush the guest cputime we spent on the guest */
> +	vtime_account_guest_exit();
>   	instrumentation_end();
>   }
>   #endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
>