linux-kernel - Re: [PATCH] x86/Hyper-V: Initialize Syn timer clock even when it's not available

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Date:   Mon, 30 Mar 2020 22:14:56 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     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
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com
Subject: Re: [PATCH] x86/Hyper-V: Initialize Syn timer clock even when it's
 not available

Sorry for wrong title. Please ignore it.

On 3/30/2020 10:09 PM, ltykernel@...il.com wrote:
> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> 
> Current code initializes clock event data structure for syn timer
> even when it's available or not. Fix it.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> ---
>   drivers/hv/hv.c | 15 +++++++++------
>   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);
>