linux-kernel - Re: [PATCH -v2] x86, tsc: Limit CPU frequency calibration on AMD

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Message-ID: <4C7448A3.2030309@zytor.com>
Date:	Tue, 24 Aug 2010 15:33:07 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Alok Kataria <akataria@...are.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	the arch/x86 maintainers <x86@...nel.org>,
	Greg KH <gregkh@...e.de>, "greg@...ah.com" <greg@...ah.com>,
	"ksrinivasan@...ell.com" <ksrinivasan@...ell.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v2] x86, tsc: Limit CPU frequency calibration on AMD

On 08/24/2010 08:53 AM, Borislav Petkov wrote:
> 6b37f5a20c0e5c334c010a587058354215433e92 introduced the CPU frequency
> calibration code for AMD CPUs whose TSCs didn't increment with the
> core's P0 frequency. From F10h, revB onward, the TSC increment rate is
> denoted by MSRC001_0015[24] and when this bit is set (which is normally
> done by the BIOS,) the TSC increments with the P0 frequency so the
> calibration is not needed and booting can be a couple of mcecs faster on
> those machines.
> 
> While at it, make the code work on 32-bit. In addition, use the 4th
> perfctr since using perfctr 0 might clash with perfctr-watchdog.c during
> LAPIC init. Finally, warn about wrongly calibrated value in the most
> seldom cases when the core TSC is not incrementing with P0 frequency.
> 
> Signed-off-by: Borislav Petkov <borislav.petkov@....com>
> ---
> 
> Here's the new version, had to change quite a lot and check all families
> first.
> 

Build failure:

/home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c: In
function ‘amd_calibrate_cpu’:
/home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:397: error:
implicit declaration of function ‘avail_to_resrv_perfctr_nmi_bit’
/home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:409: error:
implicit declaration of function ‘reserve_perfctr_nmi’
/home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:410: error:
implicit declaration of function ‘reserve_evntsel_nmi’
/home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:429: error:
implicit declaration of function ‘release_perfctr_nmi’
/home/hpa/kernel/linux-2.6-tip.cpu/arch/x86/kernel/cpu/amd.c:430: error:
implicit declaration of function ‘release_evntsel_nmi’

Reproducible by doing "make ARCH=i386 allnoconfig".

	-hpa
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