linux-kernel - Re: [PATCH 1/2] pci/irq: restore mask

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Message-ID: <86802c440804241740s53ae6587s909d307cf145d629@mail.gmail.com>
Date:	Thu, 24 Apr 2008 17:40:22 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Jesse Barnes" <jbarnes@...tuousgeek.org>,
	"David Miller" <davem@...emloft.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, tglx@...utronix.de,
	"Greg KH" <greg@...ah.com>, "Jeff Garzik" <jeff@...zik.org>,
	linux-pci <linux-pci@...ey.karlin.mff.cuni.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"James Bottomley" <James.Bottomley@...senpartnership.com>,
	"Sathya Prakash" <sathya.prakash@....com>
Subject: Re: [PATCH 1/2] pci/irq: restore mask_bits in msi shutdown -v3

On Wed, Apr 23, 2008 at 2:56 PM, Yinghai Lu <yhlu.kernel.send@...il.com> wrote:
>
>  Yinghai found after using 2.6.25-rc3 later to kexec RHEL 5.1,
>  NIC can not be used.
>
>  bisected to
>
>  | commit 89d694b9dbe769ca1004e01db0ca43964806a611
>  | Author: Thomas Gleixner <tglx@...utronix.de>
>  | Date:   Mon Feb 18 18:25:17 2008 +0100
>  |
>  |   genirq: do not leave interupts enabled on free_irq
>  |
>  |   The default_disable() function was changed in commit:
>  |
>  |    76d2160147f43f982dfe881404cfde9fd0a9da21
>  |    genirq: do not mask interrupts by default
>  |
>  |   It removed the mask function in favour of the default delayed
>  |   interrupt disabling. Unfortunately this also broke the shutdown in
>  |   free_irq() when the last handler is removed from the interrupt for
>  |   those architectures which rely on the default implementations. Now we
>  |   can end up with a enabled interrupt line after the last handler was
>  |   removed, which can result in spurious interrupts.
>  |
>  |   Fix this by adding a default_shutdown function, which is only
>  |   installed, when the irqchip implementation does provide neither a
>  |   shutdown nor a disable function.
>  |
>  |   [@stable: affected versions: .21 - .24 ]
>
>  for MSI, default_shutdown will call mask_bit for msi device.  so all mask bits
>  will left disabled after free_irq.  then if kexec next kernel that only can
>  use msi_enable bit.  all device's MSI can not be used.
>
>  want to try to restore MSI mask bits that is saved before using msi in first
>  kernel.
>
>  Eric said:
>  This is over complicated and for hardware that erroneously triggers
>  a msi irq after free_irq may have potential problems.
>
>  So lets do the much simpler, much safer, and more general method of
>  restoring the mask bit to it's pci reset defined value (enabled) when
>  we disable the kernels use of msi.
>
>  it will work, because pci_diable_msi is called after free_irq is called.
>
>  v3: extend msi_set_mask_bit to msi_set_mask_bits to take mask, so we can fully
>  restore that to 0x00 instead of 0xfe.
>
>  Signed-off-by: Yinghai Lu <yhlu.kernel@...il.com>

andrew,

this one should replace

[PATCH] x86_64: restore mask_bits in msi shutdown

in -mm

YH
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