linux-kernel - Re: [01/54] x86, vmware: Preset lpj values when on VMware.

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Date:	Sat, 14 Aug 2010 14:22:14 +0200
From:	Sven Joachim <svenjoac@....de>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Alok N Kataria <akataria@...are.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [01/54] x86, vmware: Preset lpj values when on VMware.

On 2010-08-12 02:00 +0200, Greg KH wrote:

> 2.6.34-stable review patch.  If anyone has any objections, please let us know.

Sorry for being a bit late -- I didn't get around to build 2.6.34.4-rc1
in time. :-(

> From: Alok Kataria <akataria@...are.com>
>
> commit 9f242dc10e0c3c1eb32d8c83c18650a35fd7f80d upstream.
>
> When running on VMware's platform, we have seen situations where
> the AP's try to calibrate the lpj values and fail to get good calibration
> runs becasue of timing issues. As a result delays don't work correctly
> on all cpus.
>
> The solutions is to set preset_lpj value based on the current tsc frequency
> value. This is similar to what KVM does as well.
>
> Signed-off-by: Alok N Kataria <akataria@...are.com>
> LKML-Reference: <1280790637.14933.29.camel@...32.eng.vmware.com>
> Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
>
> ---
>  arch/x86/kernel/cpu/vmware.c |    9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> --- a/arch/x86/kernel/cpu/vmware.c
> +++ b/arch/x86/kernel/cpu/vmware.c
> @@ -51,7 +51,7 @@ static inline int __vmware_platform(void
>  
>  static unsigned long vmware_get_tsc_khz(void)
>  {
> -	uint64_t tsc_hz;
> +	uint64_t tsc_hz, lpj;
>  	uint32_t eax, ebx, ecx, edx;
>  
>  	VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
> @@ -62,6 +62,13 @@ static unsigned long vmware_get_tsc_khz(
>  	printk(KERN_INFO "TSC freq read from hypervisor : %lu.%03lu MHz\n",
>  			 (unsigned long) tsc_hz / 1000,
>  			 (unsigned long) tsc_hz % 1000);
> +
> +	if (!preset_lpj) {
> +		lpj = ((u64)tsc_hz * 1000);
> +		do_div(lpj, HZ);

This led to a build failure for me because HZ is not defined in the
attached configuration.  Note that this problem did not show up in
2.6.35.2 with a very similar .config file.

> +		preset_lpj = lpj;
> +	}
> +
>  	return tsc_hz;
>  }

Regards,
        Sven



View attachment ".config" of type "text/plain" (60035 bytes)