linux-kernel - Re: [Update PATCH] x86/Hyper-V: Initialize Syn timer clock when it's

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Message-ID: <87d08t3mnn.fsf@vitty.brq.redhat.com>
Date:   Mon, 30 Mar 2020 17:09:00 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     ltykernel@...il.com
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, michael.h.kelley@...rosoft.com, wei.liu@...nel.org
Subject: Re: [Update PATCH] x86/Hyper-V: Initialize Syn timer clock when it's

ltykernel@...il.com writes:

> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>
> Current code initializes clock event data structure for syn timer
> even when it's not available. Fix it.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> ---
> - Fix the wrong title.

The new one is ... weird too :-)

I think it was supposed to be something like "x86/Hyper-V: don't
allocate clockevent device when synthetic timer is unavailable"

>  
>  drivers/hv/hv.c | 15 +++++++++------

Which tree is this patch for? Upstream clockevent allocation has moved
to drivers/clocksource/hyperv_timer.c 

>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 632d25674e7f..2e893768fc76 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -212,13 +212,16 @@ int hv_synic_alloc(void)
>  		tasklet_init(&hv_cpu->msg_dpc,
>  			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);
>  
> -		hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
> -					  GFP_KERNEL);
> -		if (hv_cpu->clk_evt == NULL) {
> -			pr_err("Unable to allocate clock event device\n");
> -			goto err;
> +		if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
> +			hv_cpu->clk_evt =
> +				kzalloc(sizeof(struct clock_event_device),
> +						  GFP_KERNEL);
> +			if (hv_cpu->clk_evt == NULL) {
> +				pr_err("Unable to allocate clock event device\n");
> +				goto err;
> +			}
> +			hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
>  		}
> -		hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
>  
>  		hv_cpu->synic_message_page =
>  			(void *)get_zeroed_page(GFP_ATOMIC);

-- 
Vitaly