Re: [PATCH 1/2] pci/irq: restore mask_bits in msi shutdown -v3

["Yinghai Lu" <yhlu.kernel@gmail.com>]

On Wed, Apr 23, 2008 at 2:56 PM, Yinghai Lu <yhlu.kernel.send@gmail.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@linutronix.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@gmail.com>

andrew,

this one should replace

[PATCH] x86_64: restore mask_bits in msi shutdown

in -mm

YH