linux-kernel - Re: [PATCH 2/5] x86: c_p_a clflush_cache

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Date:	Thu, 31 Jan 2008 13:08:29 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Huang, Ying" <ying.huang@...el.com>
Cc:	Andi Kleen <ak@...e.de>, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] x86: c_p_a clflush_cache_range fix


* Huang, Ying <ying.huang@...el.com> wrote:

> +++ b/arch/x86/kernel/cpu/common.c
> @@ -274,8 +274,10 @@ void __init cpu_detect(struct cpuinfo_x8
>  		if (c->x86 >= 0x6)
>  			c->x86_model += ((tfms >> 16) & 0xF) << 4;
>  		c->x86_mask = tfms & 15;
> -		if (cap0 & (1<<19))
> +		if (cap0 & (1<<19)) {
>  			c->x86_cache_alignment = ((misc >> 8) & 0xff) * 8;
> +			c->x86_clflush_size = ((misc >> 8) & 0xff) * 8;
> +		}

thanks!

> @@ -317,6 +319,7 @@ static void __init early_cpu_detect(void
>  	struct cpuinfo_x86 *c = &boot_cpu_data;
>  
>  	c->x86_cache_alignment = 32;
> +	c->x86_clflush_size = 32;

i suspect 32 is a good lower limit (it's not a big issue to do too 
finegrained flushes, and CLFLUSH is valid with arbitrary alignment) - 
and this will be overriden with 64 later on.

	Ingo
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