PCI: Fix the NIU MSI-X problem in a better way

The previous MSI-X fix (8d181018) had
three bugs.  First, it didn't move the write that disabled the vector.
This led to writing garbage to the MSI-X vector (spotted by Michael
Ellerman).  It didn't fix the PCI resume case, and it had a race window
where the device could generate an interrupt before the MSI-X registers
were programmed (leading to a DMA to random addresses).

Fortunately, the MSI-X capability has a bit to mask all the vectors.
By setting this bit instead of clearing the enable bit, we can ensure
the device will not generate spurious interrupts.  Since the capability
is now enabled, the NIU device will not have a problem with the reads
and writes to the MSI-X registers being in the original order in the code.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/msi.c

@@ -313,22 +313,22 @@ static void __pci_restore_msix_state(struct pci_dev *dev)
 
 	if (!dev->msix_enabled)
 		return;
+	BUG_ON(list_empty(&dev->msi_list));
+	entry = list_entry(dev->msi_list.next, struct msi_desc, list);
+	pos = entry->msi_attrib.pos;
+	pci_read_config_word(dev, pos + PCI_MSIX_FLAGS, &control);
 
 	/* route the table */
 	pci_intx_for_msi(dev, 0);
-	msix_set_enable(dev, 0);
+	control |= PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL;
+	pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
 
 	list_for_each_entry(entry, &dev->msi_list, list) {
 		write_msi_msg(entry->irq, &entry->msg);
 		msix_mask_irq(entry, entry->masked);
 	}
 
-	BUG_ON(list_empty(&dev->msi_list));
-	entry = list_entry(dev->msi_list.next, struct msi_desc, list);
-	pos = entry->msi_attrib.pos;
-	pci_read_config_word(dev, pos + PCI_MSIX_FLAGS, &control);
 	control &= ~PCI_MSIX_FLAGS_MASKALL;
-	control |= PCI_MSIX_FLAGS_ENABLE;
 	pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
 }
 
@@ -419,11 +419,14 @@ static int msix_capability_init(struct pci_dev *dev,
 	u8 bir;
 	void __iomem *base;
 
-	msix_set_enable(dev, 0);/* Ensure msix is disabled as I set it up */
-
    	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
+	pci_read_config_word(dev, pos + PCI_MSIX_FLAGS, &control);
+
+	/* Ensure MSI-X is disabled while it is set up */
+	control &= ~PCI_MSIX_FLAGS_ENABLE;
+	pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
+
 	/* Request & Map MSI-X table region */
- 	pci_read_config_word(dev, msi_control_reg(pos), &control);
 	nr_entries = multi_msix_capable(control);
 
  	pci_read_config_dword(dev, msix_table_offset_reg(pos), &table_offset);
@@ -434,7 +437,6 @@ static int msix_capability_init(struct pci_dev *dev,
 	if (base == NULL)
 		return -ENOMEM;
 
-	/* MSI-X Table Initialization */
 	for (i = 0; i < nvec; i++) {
 		entry = alloc_msi_entry(dev);
 		if (!entry)
@@ -447,7 +449,6 @@ static int msix_capability_init(struct pci_dev *dev,
 		entry->msi_attrib.default_irq = dev->irq;
 		entry->msi_attrib.pos = pos;
 		entry->mask_base = base;
-		msix_mask_irq(entry, 1);
 
 		list_add_tail(&entry->list, &dev->msi_list);
 	}
@@ -472,22 +473,31 @@ static int msix_capability_init(struct pci_dev *dev,
 		return ret;
 	}
 
+	/*
+	 * Some devices require MSI-X to be enabled before we can touch the
+	 * MSI-X registers.  We need to mask all the vectors to prevent
+	 * interrupts coming in before they're fully set up.
+	 */
+	control |= PCI_MSIX_FLAGS_MASKALL | PCI_MSIX_FLAGS_ENABLE;
+	pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
+
 	i = 0;
 	list_for_each_entry(entry, &dev->msi_list, list) {
 		entries[i].vector = entry->irq;
 		set_irq_msi(entry->irq, entry);
+		j = entries[i].entry;
+		entry->masked = readl(base + j * PCI_MSIX_ENTRY_SIZE +
+					PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
+		msix_mask_irq(entry, 1);
 		i++;
 	}
-	/* Set MSI-X enabled bits */
+
+	/* Set MSI-X enabled bits and unmask the function */
 	pci_intx_for_msi(dev, 0);
-	msix_set_enable(dev, 1);
 	dev->msix_enabled = 1;
 
-	list_for_each_entry(entry, &dev->msi_list, list) {
-		int vector = entry->msi_attrib.entry_nr;
-		entry->masked = readl(base + vector * PCI_MSIX_ENTRY_SIZE +
-					PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
-	}
+	control &= ~PCI_MSIX_FLAGS_MASKALL;
+	pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
 
 	return 0;
 }