linux-kernel - Re: [PATCH] x86: APIC: Remove apic_write

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Date:	Tue, 22 Jul 2008 15:48:32 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yong Wang <yong.y.wang@...ux.intel.com>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Zachary Amsden <zach@...are.com>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [PATCH] x86: APIC: Remove apic_write_around(); use alternatives


* Yong Wang <yong.y.wang@...ux.intel.com> wrote:

> On Mon, Jul 21, 2008 at 10:59:41AM -0700, Suresh Siddha wrote:
> > Thanks Ingo. I tested tip/master and found an issue (patch attached)
> > for x2apic support. This is not because of the recent merges we had, but
> > because of something(where we still access memory based interface after
> > enabling x2apic mode) that slipped through my earlier tests.
> > 
> > Probably it is a good idea to unmap the memory mapped interface, once we switch
> > to x2apic mode. That will catch the issues much earlier. I will
> > post another patch for this.
> > 
> > Meanwhile, I will do more testing of tip/master along with addressing
> > open issues.
> > ---
> > 
> > [patch] x64, apic: use generic apic_write() for ack_APIC_irq()
> > 
> > ack_APIC_irq() is used at too many generic places (and not just during
> > irq_chip handling!) to use the native_apic_mem_write(). For ex, this will
> > break x2apic based systems.
> > 
> > Fix ack_APIC_irq() to use the generic apic_write() even for 64-bit.
> > 
> > Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> > ---
> > 
> > diff --git a/include/asm-x86/apic.h b/include/asm-x86/apic.h
> > index 300b65e..1df955f 100644
> > --- a/include/asm-x86/apic.h
> > +++ b/include/asm-x86/apic.h
> > @@ -138,11 +138,7 @@ static inline void ack_APIC_irq(void)
> >  	 */
> >  
> >  	/* Docs say use 0 for future compatibility */
> > -#ifdef CONFIG_X86_32
> >  	apic_write(APIC_EOI, 0);
> > -#else
> > -	native_apic_mem_write(APIC_EOI, 0);
> > -#endif
> >  }
> >  
> 
> ACK. I tested this patch on my x2apic capable box and it works well. 
> Without this patch, kernel built from tip/x86/x2apic cannot boot in 
> x2apic mode and all APs got stuck in smp_callin->calibrate_delay and 
> failed to boot. After applying this patch, system boots well and all 
> processors got up and running successfully.

hm, i havent received any email from Suresh since:

   Date: Fri, 18 Jul 2008 16:18:28 -0700

something's broken in the email path ...

Could you please bounce Suresh's patch to me? (the quoted one above is 
whitespace damaged due to the reply)

	Ingo

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