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SubjectRe: [PATCH] x86_64: restore mask_bits in msi shutdown
On Fri, 11 Apr 2008 16:26:11 -0700 Yinghai Lu <yhlu.kernel.send@gmail.com> wrote:

> I can not kexec RHEL 5.1 from 2.6.25-rc3 later
>
> caused by:
> 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.
>
> So try to restore MSI mask bits that is saved before using msi in first kernel.
>
> Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
>
> Index: linux-2.6/arch/x86/kernel/io_apic_64.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/io_apic_64.c
> +++ linux-2.6/arch/x86/kernel/io_apic_64.c
> @@ -2003,6 +2003,14 @@ static void set_msi_irq_affinity(unsigne
> }
> #endif /* CONFIG_SMP */
>
> +static void msi_shutdown(unsigned int irq)
> +{
> + struct irq_desc *desc = irq_desc + irq;
> +
> + msi_restore_mask_bits(irq);
> + desc->status |= IRQ_MASKED;
> +}

I wonder if only x86_64 needs this treatment.

> Index: linux-2.6/drivers/pci/msi.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/msi.c
> +++ linux-2.6/drivers/pci/msi.c
> @@ -123,6 +123,31 @@ static void msix_flush_writes(unsigned i
> }
> }
>
> +void msi_restore_mask_bits(unsigned int irq)
> +{
> + struct msi_desc *entry;
> +
> + entry = get_irq_msi(irq);
> + BUG_ON(!entry || !entry->dev);
> + switch (entry->msi_attrib.type) {
> + case PCI_CAP_ID_MSI:
> + if (entry->msi_attrib.maskbit) {
> + int pos;
> + u32 mask_bits;
> +
> + pos = (long)entry->mask_base;
> + mask_bits = entry->orig_mask_bits;
> + pci_write_config_dword(entry->dev, pos, mask_bits);
> + }
> + break;
> + case PCI_CAP_ID_MSIX:
> + break;
> + default:
> + BUG();
> + break;
> + }
> +}

If no other architectures will ever need this, perhaps it is in the wrong
file.



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