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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Date:	Wed, 10 Oct 2012 17:01:39 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	"Zhang, Lin-Bao (Linux Kernel R&D)" <linbao.zhang@...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>
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 )

On Wed, 2012-10-10 at 16:02 -0700, Zhang, Lin-Bao (Linux Kernel R&D)
wrote:
> > As I mentioned earlier, the current design already ensures that all the IO-APIC
> > RTE's are masked between the time we enable interrupt-remapping to the time
> > when the IO-APIC RTE's are configured correctly.
> >
> > 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,
suresh

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