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Date:	Thu, 29 Mar 2007 09:41:02 -0700
From:	Mitch Williams <mitch.a.williams@...el.com>
To:	linux-pci@...ey.karlin.mff.cuni.cz
Cc:	gregkh@...e.de, ebiederm@...ssion.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	auke-jan.h.kok@...el.com
Subject: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

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.

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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