linux-kernel - Re: [PATCH] x86: smpboot - check if we have ESR register in wakeup_secondary

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Message-ID: <20080915102007.GB7131@lenovo>
Date:	Mon, 15 Sep 2008 14:20:07 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yhlu.kernel@...il.com>
Subject: Re: [PATCH] x86: smpboot - check if we have ESR register in
	wakeup_secondary_cpu

[Cyrill Gorcunov - Mon, Sep 15, 2008 at 02:01:19PM +0400]
| [Ingo Molnar - Mon, Sep 15, 2008 at 09:56:55AM +0200]
| | 
| | * Cyrill Gorcunov <gorcunov@...il.com> wrote:
| | 
| | > We should check if we have ESR register before writting to it.
| | > 
| | > Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
| | > ---
| | > 
| | > Please review!
| | > it seems the same nit in do_boot_cpu - checking now.
| | > 
| | > Index: linux-2.6.git/arch/x86/kernel/smpboot.c
| | > ===================================================================
| | > --- linux-2.6.git.orig/arch/x86/kernel/smpboot.c	2008-09-14 19:43:03.000000000 +0400
| | > +++ linux-2.6.git/arch/x86/kernel/smpboot.c	2008-09-14 21:49:36.000000000 +0400
| | > @@ -598,10 +598,12 @@ wakeup_secondary_cpu(int logical_apicid,
| | >  	 * Give the other CPU some time to accept the IPI.
| | >  	 */
| | >  	udelay(200);
| | > -	maxlvt = lapic_get_maxlvt();
| | > -	if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| | > -		apic_write(APIC_ESR, 0);
| | > -	accept_status = (apic_read(APIC_ESR) & 0xEF);
| | > +	if (APIC_INTEGRATED(apic_version[phys_apicid])) {
| | > +		maxlvt = lapic_get_maxlvt();
| | > +		if (maxlvt > 3)			/* Due to the Pentium erratum 3AP.  */
| | > +			apic_write(APIC_ESR, 0);
| | > +		accept_status = (apic_read(APIC_ESR) & 0xEF);
| | > +	}
| | >  	pr_debug("NMI sent.\n");
| | 
| | hm, is there any non-integrated lapic that has more than 3 lvts? iirc 
| | lvts were introduced with the integrated lapic.
| | 
| | 	Ingo
| | 
| 
| Yes Ingo, but don't forget the next line in former
| 
| 	accept_status = (apic_read(APIC_ESR) & 0xEF);
| 
| so we're protected in writting but _not_ in reading - which
| is buggy a bit :-)
|
| 		- Cyrill -

Ingo - could you replace in this patch message and subject -
writting to reading - it will be more correct.

		- Cyrill -
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