pci/irq: restore mask_bits in msi shutdown -v3

[PATCH 1/2] pci/irq: restore mask_bits in msi shutdown -v3

Yinghai found that kexec'ing a RHEL 5.1 kernel with 2.6.25-rc3+ kernels
prevents his NIC from working.  He bisected to

| 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
|

For MSI, default_shutdown will call mask_bit for msi device.  All mask bits
will left disabled after free_irq.  Then in the kexec case, the next kernel
can only use msi_enable bit, so all device's MSI can not be used.

So lets to restore the mask bit to its pci reset defined value (enabled) when
we disable the kernels use of msi to be a little friendlier to kexec'd kernels.

Extend msi_set_mask_bit to msi_set_mask_bits to take mask, so we can fully
restore that to 0x00 instead of 0xfe.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@hobbes.lan>

drivers/pci/msi.c

@@ -123,7 +123,7 @@ static void msix_flush_writes(unsigned int irq)
 	}
 }
 
-static void msi_set_mask_bit(unsigned int irq, int flag)
+static void msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)
 {
 	struct msi_desc *entry;
 
@@ -137,8 +137,8 @@ static void msi_set_mask_bit(unsigned int irq, int flag)
 
 			pos = (long)entry->mask_base;
 			pci_read_config_dword(entry->dev, pos, &mask_bits);
-			mask_bits &= ~(1);
-			mask_bits |= flag;
+			mask_bits &= ~(mask);
+			mask_bits |= flag & mask;
 			pci_write_config_dword(entry->dev, pos, mask_bits);
 		} else {
 			msi_set_enable(entry->dev, !flag);
@@ -241,13 +241,13 @@ void write_msi_msg(unsigned int irq, struct msi_msg *msg)
 
 void mask_msi_irq(unsigned int irq)
 {
-	msi_set_mask_bit(irq, 1);
+	msi_set_mask_bits(irq, 1, 1);
 	msix_flush_writes(irq);
 }
 
 void unmask_msi_irq(unsigned int irq)
 {
-	msi_set_mask_bit(irq, 0);
+	msi_set_mask_bits(irq, 1, 0);
 	msix_flush_writes(irq);
 }
 
@@ -291,7 +291,8 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
 	msi_set_enable(dev, 0);
 	write_msi_msg(dev->irq, &entry->msg);
 	if (entry->msi_attrib.maskbit)
-		msi_set_mask_bit(dev->irq, entry->msi_attrib.masked);
+		msi_set_mask_bits(dev->irq, entry->msi_attrib.maskbits_mask,
+				  entry->msi_attrib.masked);
 
 	pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
 	control &= ~(PCI_MSI_FLAGS_QSIZE | PCI_MSI_FLAGS_ENABLE);
@@ -315,7 +316,7 @@ static void __pci_restore_msix_state(struct pci_dev *dev)
 
 	list_for_each_entry(entry, &dev->msi_list, list) {
 		write_msi_msg(entry->irq, &entry->msg);
-		msi_set_mask_bit(entry->irq, entry->msi_attrib.masked);
+		msi_set_mask_bits(entry->irq, 1, entry->msi_attrib.masked);
 	}
 
 	BUG_ON(list_empty(&dev->msi_list));
@@ -382,6 +383,7 @@ static int msi_capability_init(struct pci_dev *dev)
 		pci_write_config_dword(dev,
 			msi_mask_bits_reg(pos, is_64bit_address(control)),
 			maskbits);
+		entry->msi_attrib.maskbits_mask = temp;
 	}
 	list_add_tail(&entry->list, &dev->msi_list);
 
@@ -583,6 +585,11 @@ void pci_disable_msi(struct pci_dev* dev)
 
 	BUG_ON(list_empty(&dev->msi_list));
 	entry = list_entry(dev->msi_list.next, struct msi_desc, list);
+	/* Return the the pci reset with msi irqs unmasked */
+	if (entry->msi_attrib.maskbit) {
+		u32 mask = entry->msi_attrib.maskbits_mask;
+		msi_set_mask_bits(dev->irq, mask, ~mask);
+	}
 	if (!entry->dev || entry->msi_attrib.type != PCI_CAP_ID_MSI) {
 		return;
 	}

include/linux/msi.h

@@ -22,6 +22,7 @@ struct msi_desc {
 		__u8	masked	: 1;
 		__u8	is_64	: 1;	/* Address size: 0=32bit 1=64bit  */
 		__u8	pos;	 	/* Location of the msi capability */
+		__u32	maskbits_mask;  /* mask bits mask */
 		__u16	entry_nr;    	/* specific enabled entry 	  */
 		unsigned default_irq;	/* default pre-assigned irq	  */
 	}msi_attrib;