linux-kernel - RE: [PATCH] x86, hyperv: bypass the timer_irq

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Message-ID: <29a02b00af824078acad392c537def36@BY2PR03MB299.namprd03.prod.outlook.com>
Date:	Fri, 24 Jan 2014 21:16:18 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Jason Wang <jasowang@...hat.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] x86, hyperv: bypass the timer_irq_works() check



> -----Original Message-----
> From: Jason Wang [mailto:jasowang@...hat.com]
> Sent: Thursday, January 23, 2014 10:03 PM
> To: KY Srinivasan; Haiyang Zhang; tglx@...utronix.de; mingo@...hat.com;
> hpa@...or.com; x86@...nel.org; devel@...uxdriverproject.org; linux-
> kernel@...r.kernel.org
> Cc: Jason Wang
> Subject: [PATCH] x86, hyperv: bypass the timer_irq_works() check
> 
> This patch bypass the timer_irq_works() check for hyperv guest since:
> 
> - It was guaranteed to work.
> - timer_irq_works() may fail sometime due to the lpj calibration were inaccurate
>   in a hyperv guest or a buggy host.
> 
> In the future, we should get the tsc frequency from hypervisor and use preset
> lpj instead.
> 
> Cc: K. Y. Srinivasan <kys@...rosoft.com>
> Cc: Haiyang Zhang <haiyangz@...rosoft.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Thanks Jason.
Acked-by: K. Y. Srinivasan <kys@...rosoft.com>
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 9f7ca26..832d05a 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -26,6 +26,7 @@
>  #include <asm/irq_regs.h>
>  #include <asm/i8259.h>
>  #include <asm/apic.h>
> +#include <asm/timer.h>
> 
>  struct ms_hyperv_info ms_hyperv;
>  EXPORT_SYMBOL_GPL(ms_hyperv);
> @@ -105,6 +106,11 @@ static void __init ms_hyperv_init_platform(void)
> 
>  	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
>  		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
> +
> +#ifdef CONFIG_X86_IO_APIC
> +	no_timer_check = 1;
> +#endif
> +
>  }
> 
>  const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
> --
> 1.8.3.2

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