linux-kernel - Re: [PATCH] k8: Enable legacy irqs with extended cpu ids

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Date:	Wed, 12 Dec 2007 01:43:31 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Neil Horman <nhorman@...driver.com>
Cc:	Yinghai Lu <yhlu.kernel@...il.com>,
	Ben Woodard <woodard@...hat.com>,
	Neil Horman <nhorman@...hat.com>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...e.de>,
	hbabu@...ibm.com, Andi Kleen <andi@...stfloor.org>,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com
Subject: Re: [PATCH] k8: Enable legacy irqs with  extended cpu ids

Neil Horman <nhorman@...driver.com> writes:

> Recently a kdump bug was discovered in which a system would hang inside
> calibrate_delay during the booting of the kdump kernel.  This was caused by the
> fact that the jiffies counter was not being incremented during timer
> calibration.  The root cause of this problem was found to be a bios
> misconfiguration of the hypertransport bus.  On system affected by this hang,
> the bios had assigned APIC ids which used extended apic bits (more than the
> nominal 4 bit ids's), but failed to configure bit 17 of the hypertransport
> transaction config register, which indicated that the mask for the destination
> field of interrupt packets accross the ht bus (see section 3.3.9 of
> http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26094.PDF).
> If a crash occurs on a cpu with an APIC id that extends beyond 4 bits, it will
> not recieve interrupts during the kdump kernel boot, and this hang will be the
> result.  The fix is to add this patch, whcih add an early pci quirk check, to
> forcibly enable this bit in the httcfg register.  This enables all cpus on a
> system to receive interrupts, and allows kdump kernel bootup to procede
> normally.
>
> Regards
> Neil
>
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>

Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Eric
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