Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Yury Norov <yury.norov@gmail.com>, linux-kernel@vger.kernel.org,
        Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, kvm@vger.kernel.org
Cc:     Yury Norov <yury.norov@gmail.com>, Jan Kara <jack@suse.cz>,
        Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr>,
        Matthew Wilcox <willy@infradead.org>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>,
        Alexey Klimov <klimov.linux@gmail.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Sergey Shtylyov <s.shtylyov@omp.ru>
Subject: Re: [PATCH v2 13/35] KVM: x86: hyper-v: optimize and cleanup
 kvm_hv_process_stimers()
In-Reply-To: <20231203193307.542794-12-yury.norov@gmail.com>
References: <20231203192422.539300-1-yury.norov@gmail.com>
 <20231203193307.542794-1-yury.norov@gmail.com>
 <20231203193307.542794-12-yury.norov@gmail.com>
Date:   Mon, 04 Dec 2023 10:53:05 +0100
Message-ID: <87h6kymgzi.fsf@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Yury Norov <yury.norov@gmail.com> writes:

> The function traverses stimer_pending_bitmap in a for-loop bit by bit.
> We can do it faster by using atomic find_and_set_bit().
>
> While here, refactor the logic by decreasing indentation level.
>
> CC: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
>  arch/x86/kvm/hyperv.c | 39 +++++++++++++++++++--------------------
>  1 file changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 238afd7335e4..a0e45d20d451 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -870,27 +870,26 @@ void kvm_hv_process_stimers(struct kvm_vcpu *vcpu)
>  	if (!hv_vcpu)
>  		return;
>  
> -	for (i = 0; i < ARRAY_SIZE(hv_vcpu->stimer); i++)
> -		if (test_and_clear_bit(i, hv_vcpu->stimer_pending_bitmap)) {
> -			stimer = &hv_vcpu->stimer[i];
> -			if (stimer->config.enable) {
> -				exp_time = stimer->exp_time;
> -
> -				if (exp_time) {
> -					time_now =
> -						get_time_ref_counter(vcpu->kvm);
> -					if (time_now >= exp_time)
> -						stimer_expiration(stimer);
> -				}
> -
> -				if ((stimer->config.enable) &&
> -				    stimer->count) {
> -					if (!stimer->msg_pending)
> -						stimer_start(stimer);
> -				} else
> -					stimer_cleanup(stimer);
> -			}
> +	for_each_test_and_clear_bit(i, hv_vcpu->stimer_pending_bitmap,
> +					ARRAY_SIZE(hv_vcpu->stimer)) {
> +		stimer = &hv_vcpu->stimer[i];
> +		if (!stimer->config.enable)
> +			continue;
> +
> +		exp_time = stimer->exp_time;
> +
> +		if (exp_time) {
> +			time_now = get_time_ref_counter(vcpu->kvm);
> +			if (time_now >= exp_time)
> +				stimer_expiration(stimer);
>  		}
> +
> +		if (stimer->config.enable && stimer->count) {
> +			if (!stimer->msg_pending)
> +				stimer_start(stimer);
> +		} else
> +			stimer_cleanup(stimer);

Minor nitpick: it's better (and afair required by coding style) to use
'{}' for both branches here:

	if (stimer->config.enable && stimer->count) {
		if (!stimer->msg_pending)
			stimer_start(stimer);
	} else {
		stimer_cleanup(stimer);
	}

> +	}
>  }
>  
>  void kvm_hv_vcpu_uninit(struct kvm_vcpu *vcpu)

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

-- 
Vitaly