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PCI: MSI: Remove unsafe and unnecessary hardware access

Message ID 1276802196.2083.12.camel@achroite.uk.solarflarecom.com (mailing list archive)
State Accepted, archived
Headers show

Commit Message

Ben Hutchings June 17, 2010, 7:16 p.m. UTC
None
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Patch

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 77b68ea..03f04dc 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -196,30 +196,15 @@  void unmask_msi_irq(unsigned int irq)
 void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
 {
 	struct msi_desc *entry = get_irq_desc_msi(desc);
-	if (entry->msi_attrib.is_msix) {
-		void __iomem *base = entry->mask_base +
-			entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;
 
-		msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR);
-		msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR);
-		msg->data = readl(base + PCI_MSIX_ENTRY_DATA);
-	} else {
-		struct pci_dev *dev = entry->dev;
-		int pos = entry->msi_attrib.pos;
-		u16 data;
+	/* We do not touch the hardware (which may not even be
+	 * accessible at the moment) but return the last message
+	 * written.  Assert that this is valid, assuming that
+	 * valid messages are not all-zeroes. */
+	BUG_ON(!(entry->msg.address_hi | entry->msg.address_lo |
+		 entry->msg.data));
 
-		pci_read_config_dword(dev, msi_lower_address_reg(pos),
-					&msg->address_lo);
-		if (entry->msi_attrib.is_64) {
-			pci_read_config_dword(dev, msi_upper_address_reg(pos),
-						&msg->address_hi);
-			pci_read_config_word(dev, msi_data_reg(pos, 1), &data);
-		} else {
-			msg->address_hi = 0;
-			pci_read_config_word(dev, msi_data_reg(pos, 0), &data);
-		}
-		msg->data = data;
-	}
+	*msg = entry->msg;
 }
 
 void read_msi_msg(unsigned int irq, struct msi_msg *msg)
@@ -232,7 +217,10 @@  void read_msi_msg(unsigned int irq, struct msi_msg *msg)
 void write_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
 {
 	struct msi_desc *entry = get_irq_desc_msi(desc);
-	if (entry->msi_attrib.is_msix) {
+
+	if (entry->dev->current_state != PCI_D0) {
+		/* Don't touch the hardware now */
+	} else if (entry->msi_attrib.is_msix) {
 		void __iomem *base;
 		base = entry->mask_base +
 			entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;