linux-kernel - RE: [PATCH] fix x2apic defect that Linux kernel doesn't mask 8259A interrupt during the time window between changing VT-d table base address and initializing these VT-d entries(smpboot.c and apic.c )

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Message-ID: <92645B27BF79D04FBD2B0F8494FFD0F9102B85@G2W2429.americas.hpqcorp.net>
Date:	Thu, 11 Oct 2012 16:46:29 +0000
From:	"Zhang, Lin-Bao (Linux Kernel R&D)" <linbao.zhang@...com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alan@...rguk.ukuu.org.uk" <alan@...rguk.ukuu.org.uk>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"Croxon, Nigel" <nigel.croxon@...com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"Sakkinen, Jarkko" <jarkko.sakkinen@...el.com>,
	"joerg.roedel@....com" <joerg.roedel@....com>,
	"agordeev@...hat.com" <agordeev@...hat.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"Zhang, Lin-Bao (Linux Kernel R&D)" <linbao.zhang@...com>
Subject: RE: [PATCH] fix x2apic defect that Linux kernel doesn't mask 8259A
 interrupt during the time window between changing VT-d table base address
 and initializing these VT-d entries(smpboot.c and apic.c )


> -----Original Message-----
> From: Suresh Siddha [mailto:suresh.b.siddha@...el.com]
> Sent: 2012年10月10日 18:02
> > > So I looked at why you are seeing the problem with v2.6.32 but not
> > > with the recent kernels. And I think I found out the reason.
> >
> > I want to know what masking IO-APIC means?
> 
> As the platform is configured to use virtual-wire B and the corresponding
> IO-APIC RTE is masked, that interrupt will be dropped.
> 
thanks for your explanation and confirm, I also consulted BIOS guys , 
yes, interrupt will be dropped , software didn't see them,and don't go to handle them. 
So we OS don't need to disable 8259A interrupt during the window 
, only if 2.6.32 has applied your patch(triggered some actions to mask IO-apic)
That's good. Perfect design . thanks.

Here we go!
  
---------------
-- Bob(LinBao Zhang)
HP linux kernel enginner