linux-kernel - Re: [PATCH 8/20] x86_64: Add EFER to the set registers saved by save_processor

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Date:	Sat, 18 Nov 2006 01:11:29 +0100
From:	Pavel Machek <pavel@....cz>
To:	Vivek Goyal <vgoyal@...ibm.com>
Cc:	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Reloc Kernel List <fastboot@...ts.osdl.org>,
	ebiederm@...ssion.com, akpm@...l.org, ak@...e.de, hpa@...or.com,
	magnus.damm@...il.com, lwang@...hat.com, dzickus@...hat.com,
	rjw@...k.pl
Subject: Re: [PATCH 8/20] x86_64: Add EFER to the set registers saved by save_processor_state

Hi!

> EFER varies like %cr4 depending on the cpu capabilities, and which cpu
> capabilities we want to make use of.  So save/restore it make certain
> we have the same EFER value when we are done.

I still think that comment is right: EFER is function(cpu
capabilities, kernel version, kernel cmdline); and that _should_ be
constant accross suspend.

Anyway saving it does not hurt and code is probably easier to
understand.

ACK.
								Pavel


>  	/* XMM0..XMM15 should be handled by kernel_fpu_begin(). */
> -	/* EFER should be constant for kernel version, no need to handle it. */
>  	/*
>  	 * segment registers
>  	 */
> @@ -50,6 +49,7 @@ void __save_processor_state(struct saved
>  	/*
>  	 * control registers 
>  	 */
> +	rdmsrl(MSR_EFER, ctxt->efer);
>  	asm volatile ("movq %%cr0, %0" : "=r" (ctxt->cr0));
>  	asm volatile ("movq %%cr2, %0" : "=r" (ctxt->cr2));
>  	asm volatile ("movq %%cr3, %0" : "=r" (ctxt->cr3));
> @@ -75,6 +75,7 @@ void __restore_processor_state(struct sa
>  	/*
>  	 * control registers
>  	 */
> +	wrmsrl(MSR_EFER, ctxt->efer);
>  	asm volatile ("movq %0, %%cr8" :: "r" (ctxt->cr8));
>  	asm volatile ("movq %0, %%cr4" :: "r" (ctxt->cr4));
>  	asm volatile ("movq %0, %%cr3" :: "r" (ctxt->cr3));
> --- linux-2.6.19-rc6-reloc/include/asm-x86_64/suspend.h~x86_64-Add-EFER-to-the-set-registers-saved-by-save_processor_state	2006-11-17 00:08:16.000000000 -0500
> @@ -17,6 +17,7 @@ struct saved_context {
>    	u16 ds, es, fs, gs, ss;
>  	unsigned long gs_base, gs_kernel_base, fs_base;
>  	unsigned long cr0, cr2, cr3, cr4, cr8;
> +	unsigned long efer;
>  	u16 gdt_pad;
>  	u16 gdt_limit;
>  	unsigned long gdt_base;
> _

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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