From: Simon Horman <horms@verge.net.au>
To: Neil Horman <nhorman@tuxdriver.com>
Cc: linux-pci@vger.kernel.org, kexec@lists.infradead.org,
vgoyal@redhat.com, jbarnes@virtuousgeek.org
Subject: Re: [PATCH] pci: add quirk for non-symmetric-mode irq routing to versions 0 and 4 of the MCP55 northbridge
Date: Wed, 22 Sep 2010 09:44:48 +0900 [thread overview]
Message-ID: <20100922004448.GI3243@verge.net.au> (raw)
In-Reply-To: <20100921175439.GA21044@hmsreliant.think-freely.org>
On Tue, Sep 21, 2010 at 01:54:39PM -0400, Neil Horman wrote:
> A long time ago I worked on a RHEL5 bug in which kdump hung during boot
> on a set of systems. The systems hung because they never received timer
> interrupts during calibrate_delay. These systems also all had Opteron
> processors on a hypertransport bus, bridged to a pci bus via an Nvidia MCP55
> northbridge chip. AFter much wrangling I managed to learn from Nvidia that they
> have an undocumented register in some versions of that chip which control how
> legacy interrupts are send to the cpu complex when the ioapic isn't active.
> Nvidia defaults this register to only send legacy interrupts to the BSP, so if
> kdump happens to boot on an AP, we never get timer interrupts and boom. I had
> initially used this quirk as a workaround, with my intent being to move apic
> initalization to an earlier point in the boot process, so the setting of the
> register would be irrelevant. Given the work involved in doing that however,
> the fragile nature of the apic initalization code, and the fact that, over the 2
> years since we found this bug, the MCP55 is the only chip which seems to have
> this issue, I've figure at this point its likely safer to just carry the quirk
> around. By setting the referenced bits in this hidden register, interrupts will
> be broadcast to all cpus when the ioapic isn't active on the above described
> systems.
>
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
FWIW, Acked-by: Simon Horman <horms@verge.net.au>
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next prev parent reply other threads:[~2010-09-22 0:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-21 17:54 [PATCH] pci: add quirk for non-symmetric-mode irq routing to versions 0 and 4 of the MCP55 northbridge Neil Horman
2010-09-22 0:44 ` Simon Horman [this message]
2010-09-22 13:14 ` Vivek Goyal
2010-09-24 16:54 ` Jesse Barnes
2010-09-24 17:40 ` Neil Horman
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