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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Joao Martins <joao.m.martins@oracle.com>, xen-devel@lists.xen.org
Cc: Keir Fraser <keir@xen.org>, Jan Beulich <jbeulich@suse.com>
Subject: Re: [PATCH 3/5] x86/time: streamline platform time init on plt_init()
Date: Fri, 18 Mar 2016 20:32:48 +0000	[thread overview]
Message-ID: <56EC65F0.3090607@citrix.com> (raw)
In-Reply-To: <1458231136-13457-4-git-send-email-joao.m.martins@oracle.com>

On 17/03/16 16:12, Joao Martins wrote:
> And use to initialize platform time solely for clocksource=tsc,
> as opposed to initializing platform overflow timer, which would
> only fire in ~180 years (on 2.2 Ghz Broadwell processor).
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>

Again, just style corrections.

Reviewed-by Andrew Cooper <andrew.cooper3@citrix.com>

> diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
> index 1311c58..5af8902 100644
> --- a/xen/arch/x86/time.c
> +++ b/xen/arch/x86/time.c
> @@ -434,6 +434,7 @@ uint64_t ns_to_acpi_pm_tick(uint64_t ns)
>  /************************************************************
>   * PLATFORM TIMER 4: TSC
>   */
> +static bool_t clocksource_is_tsc = 0;

No need to explicitly initialise to 0.

>  static u64 tsc_freq;
>  static unsigned long tsc_max_warp;
>  static void tsc_check_reliability(void);
> @@ -466,7 +467,7 @@ static int __init init_tsctimer(struct platform_timesource *pts)
>      }
>  
>      pts->frequency = tsc_freq;
> -    return tsc_reliable;
> +    return ( clocksource_is_tsc = tsc_reliable );

While this does work, please avoid mixing an assignment and a return.

Something like

pts->frequency = tsc_freq;
clocksource_is_tsc = tsc_reliable;

return tsc_reliable;

is fine and easier logic to read.

> @@ -633,11 +648,22 @@ static void __init init_platform_timer(void)
>  
>      set_time_scale(&plt_scale, pts->frequency);
>  
> -    plt_overflow_period = scale_delta(
> -        1ull << (pts->counter_bits-1), &plt_scale);
> -    init_timer(&plt_overflow_timer, plt_overflow, NULL, 0);
>      plt_src = *pts;
> -    plt_overflow(NULL);
> +
> +    if ( clocksource_is_tsc )
> +    {
> +        plt_init();
> +    }
> +    else
> +    {
> +        plt_overflow_period = scale_delta(
> +            1ull << (pts->counter_bits-1), &plt_scale);

As you are moving this codeblock, please fix the style to
(pts->counter_bits - 1)

~Andrew

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  reply	other threads:[~2016-03-18 20:32 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17 16:12 [PATCH 0/5] x86/time: PVCLOCK_TSC_STABLE_BIT support Joao Martins
2016-03-17 16:12 ` [PATCH 1/5] public/xen.h: add flags field to vcpu_time_info Joao Martins
2016-03-18 20:12   ` Andrew Cooper
2016-03-21 11:42     ` Joao Martins
2016-03-21 11:43       ` Andrew Cooper
2016-03-21 11:51         ` Joao Martins
2016-03-21 15:10   ` Jan Beulich
2016-03-21 15:27     ` Andrew Cooper
2016-03-21 15:40       ` Joao Martins
2016-03-17 16:12 ` [PATCH 2/5] x86/time: implement tsc as clocksource Joao Martins
2016-03-18 20:21   ` Andrew Cooper
2016-03-21 11:43     ` Joao Martins
2016-03-22 12:41     ` Joao Martins
2016-03-22 12:46       ` Jan Beulich
2016-03-22 15:51         ` Joao Martins
2016-03-22 16:02           ` Jan Beulich
2016-03-22 20:40             ` Joao Martins
2016-03-23  7:28               ` Jan Beulich
2016-03-23 12:05                 ` Joao Martins
2016-03-23 14:05                   ` Jan Beulich
2016-03-17 16:12 ` [PATCH 3/5] x86/time: streamline platform time init on plt_init() Joao Martins
2016-03-18 20:32   ` Andrew Cooper [this message]
2016-03-21 11:45     ` Joao Martins
2016-03-17 16:12 ` [PATCH 4/5] x86/time: refactor read_platform_stime() Joao Martins
2016-03-18 20:34   ` Andrew Cooper
2016-03-21 11:45     ` Joao Martins
2016-03-21 13:08       ` Andrew Cooper
2016-03-17 16:12 ` [PATCH 5/5] x86/time: implement PVCLOCK_TSC_STABLE_BIT Joao Martins
2016-03-18 20:58   ` Andrew Cooper
2016-03-21 11:50     ` Joao Martins

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