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Message-ID: <m1hcs4j88u.fsf@ebiederm.dsl.xmission.com>
Date: Thu, 29 Mar 2007 10:59:45 -0600
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Mitch Williams <mitch.a.williams@...el.com>
Cc: linux-pci@...ey.karlin.mff.cuni.cz, gregkh@...e.de,
ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
akpm@...ux-foundation.org, auke-jan.h.kok@...el.com
Subject: Re: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)
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/unmask and rebalancing operations.
>
> This patch has been validated with (unreleased) network hardware which
> uses MSI-X.
>
> Revised with input from Eric Biederman.
Do we still need the flush the set affinity routines?
Shouldn't flush in mask and unmask should now be enough?
>
> Signed-off-by: Mitch Williams <mitch.a.williams@...el.com>
>
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/i386/kernel/io_apic.c
> linux-2.6.21-rc5/arch/i386/kernel/io_apic.c
> --- linux-2.6.21-rc5-clean/arch/i386/kernel/io_apic.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/i386/kernel/io_apic.c 2007-03-28 10:19:14.000000000
> -0700
> @@ -2584,6 +2584,7 @@ static void set_msi_irq_affinity(unsigne
> msg.address_lo |= MSI_ADDR_DEST_ID(dest);
>
> write_msi_msg(irq, &msg);
> + msix_flush_writes(irq);
> irq_desc[irq].affinity = mask;
> }
> #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/ia64/kernel/msi_ia64.c
> linux-2.6.21-rc5/arch/ia64/kernel/msi_ia64.c
> --- linux-2.6.21-rc5-clean/arch/ia64/kernel/msi_ia64.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/ia64/kernel/msi_ia64.c 2007-03-28 09:34:27.000000000
> -0700
> @@ -60,6 +60,7 @@ static void ia64_set_msi_irq_affinity(un
> msg.address_lo = addr;
>
> write_msi_msg(irq, &msg);
> + msix_flush_writes(irq);
> irq_desc[irq].affinity = cpu_mask;
> }
> #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/ia64/sn/kernel/msi_sn.c
> linux-2.6.21-rc5/arch/ia64/sn/kernel/msi_sn.c
> --- linux-2.6.21-rc5-clean/arch/ia64/sn/kernel/msi_sn.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/ia64/sn/kernel/msi_sn.c 2007-03-28 09:34:06.000000000
> -0700
> @@ -204,6 +204,7 @@ static void sn_set_msi_irq_affinity(unsi
> msg.address_lo = (u32)(bus_addr & 0x00000000ffffffff);
>
> write_msi_msg(irq, &msg);
> + msix_flush_writes(irq);
> irq_desc[irq].affinity = cpu_mask;
> }
> #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/x86_64/kernel/io_apic.c
> linux-2.6.21-rc5/arch/x86_64/kernel/io_apic.c
> --- linux-2.6.21-rc5-clean/arch/x86_64/kernel/io_apic.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/x86_64/kernel/io_apic.c 2007-03-28 10:18:52.000000000
> -0700
> @@ -1956,6 +1956,7 @@ static void set_msi_irq_affinity(unsigne
> msg.address_lo |= MSI_ADDR_DEST_ID(dest);
>
> write_msi_msg(irq, &msg);
> + msix_flush_writes(irq);
> irq_desc[irq].affinity = mask;
> }
> #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/drivers/pci/msi.c
> linux-2.6.21-rc5/drivers/pci/msi.c
> --- linux-2.6.21-rc5-clean/drivers/pci/msi.c 2007-03-28 10:05:24.000000000 -0700
> +++ linux-2.6.21-rc5/drivers/pci/msi.c 2007-03-28 09:21:34.000000000 -0700
> @@ -68,6 +68,29 @@ static void msix_set_enable(struct pci_d
> }
> }
>
> +void msix_flush_writes(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:
> + /* nothing to do */
> + break;
> + case PCI_CAP_ID_MSIX:
> + {
> + int offset = entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
> + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET;
> + readl(entry->mask_base + offset);
> + break;
> + }
> + default:
> + BUG();
> + break;
> + }
> +}
> +
> static void msi_set_mask_bit(unsigned int irq, int flag)
> {
> struct msi_desc *entry;
> @@ -186,11 +209,13 @@ void write_msi_msg(unsigned int irq, str
> void mask_msi_irq(unsigned int irq)
> {
> msi_set_mask_bit(irq, 1);
> + msix_flush_writes(irq);
> }
>
> void unmask_msi_irq(unsigned int irq)
> {
> msi_set_mask_bit(irq, 0);
> + msix_flush_writes(irq);
> }
>
> static int msi_free_irq(struct pci_dev* dev, int irq);
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/include/linux/msi.h
> linux-2.6.21-rc5/include/linux/msi.h
> --- linux-2.6.21-rc5-clean/include/linux/msi.h 2007-03-28 10:05:25.000000000
> -0700
> +++ linux-2.6.21-rc5/include/linux/msi.h 2007-03-28 09:21:51.000000000 -0700
> @@ -12,6 +12,7 @@ extern void mask_msi_irq(unsigned int ir
> extern void unmask_msi_irq(unsigned int irq);
> extern void read_msi_msg(unsigned int irq, struct msi_msg *msg);
> extern void write_msi_msg(unsigned int irq, struct msi_msg *msg);
> +extern void msix_flush_writes(unsigned int irq);
>
> struct msi_desc {
> struct {
-
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