linux-kernel - Re: [PATCH -mm] IOAT: fix for UP use of cpu_physical

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Date:	Mon, 20 Aug 2007 15:26:59 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Shannon Nelson <shannon.nelson@...el.com>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	chris.leech@...il.com, ak@...e.de, tony.luck@...el.com
Subject: Re: [PATCH -mm] IOAT: fix for UP use of cpu_physical_id()

Shannon Nelson wrote:
> Make sure we can use cpu_physical_id() even when compiled for
> uni-processor.
> 
> diff --git a/drivers/dma/ioat_dca.c b/drivers/dma/ioat_dca.c
> index c3a500b..b1af49c 100644
> --- a/drivers/dma/ioat_dca.c
> +++ b/drivers/dma/ioat_dca.c
> @@ -25,6 +25,14 @@
>  #include <linux/smp.h>
>  #include <linux/interrupt.h>
>  #include <linux/dca.h>
> +
> +// either a kernel change is needed, or we need something like this in kernel
> +#ifndef CONFIG_SMP
> +#include <asm/smp.h>
> +#undef cpu_physical_id
> +#define cpu_physical_id(cpu) (cpuid_ebx(1) >> 24)
> +#endif
> +

This value should probably be cached.  Executing cpuid to get a static
value seems like a bad idea.

	-hpa
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