linux-kernel - Re: [patch] x86, tlb: switch cr3 in leave

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Message-ID: <4F6BC1C4.6050502@zytor.com>
Date:	Thu, 22 Mar 2012 17:20:20 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86, tlb: switch cr3 in leave_mm() only when needed

On 03/22/2012 05:01 PM, Suresh Siddha wrote:
> 
> Agreed. Updated patch appended. Thanks.
> ---
> From: Suresh Siddha <suresh.b.siddha@...el.com>
> Subject: x86, tlb: switch cr3 in leave_mm() only when needed
> 
> Currently leave_mm() unconditionally switches the cr3 to swapper_pg_dir.
> But there is no need to change the cr3, if we already left that mm.
> 
> intel_idle() for example calls leave_mm() on every deep c-state entry where
> the CPU flushes the TLB for us. Similarly flush_tlb_all() was also calling
> leave_mm() whenever the TLB is in LAZY state. Both these paths will be
> improved with this change.
> 
> Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> 

Looks great to me.  Linus, do you want this one later in the window if
it tests out OK between now and then, or is it too late?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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