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    SubjectRe: [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@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


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