linux-kernel - Re: [PATCH 2.6.21-rc5] Flush MSI-X table writes (rev 3)

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Message-Id: <20070330124747.f20c9eb0.akpm@linux-foundation.org>
Date:	Fri, 30 Mar 2007 12:47:47 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	Mitch Williams <mitch.a.williams@...el.com>,
	linux-pci@...ey.karlin.mff.cuni.cz, gregkh@...e.de,
	linux-kernel@...r.kernel.org, auke-jan.h.kok@...el.com
Subject: Re: [PATCH 2.6.21-rc5] Flush MSI-X table writes (rev 3)

On Fri, 30 Mar 2007 13:04:02 -0600
ebiederm@...ssion.com (Eric W. Biederman) wrote:

> Mitch Williams <mitch.a.williams@...el.com> writes:
> 
> > This patch fixes a kernel bug which is triggered when using the
> > irqbalance daemon with MSI-X hardware.
> >
> > Because both MSI-X interrupt messages and MSI-X table writes are posted,
> > it's possible for them to cross while in-flight.  This results in
> > interrupts being received long after the kernel thinks they're disabled,
> > and in interrupts being sent to stale vectors after rebalancing.
> >
> > This patch performs a read flush after writes to the MSI-X table for
> > mask and unmask operations.  Since the SMP affinity is set while
> > the interrupt is masked, and since it's unmasked immediately after,
> > no additional flushes are required in the various affinity setting
> > routines.
> >
> > This patch has been validated with (unreleased) network hardware which
> > uses MSI-X.
> >
> > Revised with input from Eric Biederman.
> 
> Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Did we end up deciding whether this is (needed*safe) enough for 2.6.21?
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