[PATCH 2/3] msi: Fixup the msi enable/disable logic

[Eric W. Biederman]

enable/disable_msi_mode have several side effects which keeps them from
being generally useful.  So this patch replaces them with with two
much more targeted functions: msi_set_enable and msix_set_enable.

This patch makes pci_dev->msi_enabled and pci_dev->msix_enabled the
definitive way to test if linux has enabled the msi capability, and
has the appropriate msi data structures set up.

This patch ensures that while writing the msi messages in save/restore
and during device initialization we have the msi capability disabled
so we don't get into races.  The pci spec requires that we do not have
the msi capability enabled and the msi messages unmasked while we write
the messages.  Completely disabling the capability is overkill but it
is easy :)

Care has been taken so we never have both a msi capability and intx
enabled simultaneously.  We haven't run into a problem yet but better
safe then sorry.

Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
 drivers/pci/msi.c |  144 +++++++++++++++++++++++-----------------------------
 1 files changed, 64 insertions(+), 80 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index fd1068b..c43e7d2 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -38,6 +38,36 @@ static int msi_cache_init(void)
 	return 0;
 }
 
+static void msi_set_enable(struct pci_dev *dev, int enable)
+{
+	int pos;
+	u16 control;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
+	if (pos) {
+		pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
+		control &= ~PCI_MSI_FLAGS_ENABLE;
+		if (enable)
+			control |= PCI_MSI_FLAGS_ENABLE;
+		pci_write_config_word(dev, pos + PCI_MSI_FLAGS, control);
+	}
+}
+
+static void msix_set_enable(struct pci_dev *dev, int enable)
+{
+	int pos;
+	u16 control;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
+	if (pos) {
+		pci_read_config_word(dev, pos + PCI_MSIX_FLAGS, &control);
+		control &= ~PCI_MSIX_FLAGS_ENABLE;
+		if (enable)
+			control |= PCI_MSIX_FLAGS_ENABLE;
+		pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
+	}
+}
+
 static void msi_set_mask_bit(unsigned int irq, int flag)
 {
 	struct msi_desc *entry;
@@ -192,44 +222,6 @@ static struct msi_desc* alloc_msi_entry(void)
 	return entry;
 }
 
-static void enable_msi_mode(struct pci_dev *dev, int pos, int type)
-{
-	u16 control;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (type == PCI_CAP_ID_MSI) {
-		/* Set enabled bits to single MSI & enable MSI_enable bit */
-		msi_enable(control, 1);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msi_enabled = 1;
-	} else {
-		msix_enable(control);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msix_enabled = 1;
-	}
-
-	pci_intx(dev, 0);  /* disable intx */
-}
-
-static void disable_msi_mode(struct pci_dev *dev, int pos, int type)
-{
-	u16 control;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (type == PCI_CAP_ID_MSI) {
-		/* Set enabled bits to single MSI & enable MSI_enable bit */
-		msi_disable(control);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msi_enabled = 0;
-	} else {
-		msix_disable(control);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msix_enabled = 0;
-	}
-
-	pci_intx(dev, 1);  /* enable intx */
-}
-
 #ifdef CONFIG_PM
 static int __pci_save_msi_state(struct pci_dev *dev)
 {
@@ -238,12 +230,11 @@ static int __pci_save_msi_state(struct pci_dev *dev)
 	struct pci_cap_saved_state *save_state;
 	u32 *cap;
 
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
-	if (pos <= 0 || dev->no_msi)
+	if (!dev->msi_enabled)
 		return 0;
 
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSI_FLAGS_ENABLE))
+	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
+	if (pos <= 0)
 		return 0;
 
 	save_state = kzalloc(sizeof(struct pci_cap_saved_state) + sizeof(u32) * 5,
@@ -276,13 +267,18 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
 	struct pci_cap_saved_state *save_state;
 	u32 *cap;
 
+	if (!dev->msi_enabled)
+		return;
+
 	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_MSI);
 	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
 	if (!save_state || pos <= 0)
 		return;
 	cap = &save_state->data[0];
 
+	pci_intx(dev, 0);		/* disable intx */
 	control = cap[i++] >> 16;
+	msi_set_enable(dev, 0);
 	pci_write_config_dword(dev, pos + PCI_MSI_ADDRESS_LO, cap[i++]);
 	if (control & PCI_MSI_FLAGS_64BIT) {
 		pci_write_config_dword(dev, pos + PCI_MSI_ADDRESS_HI, cap[i++]);
@@ -292,7 +288,6 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
 	if (control & PCI_MSI_FLAGS_MASKBIT)
 		pci_write_config_dword(dev, pos + PCI_MSI_MASK_BIT, cap[i++]);
 	pci_write_config_word(dev, pos + PCI_MSI_FLAGS, control);
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSI);
 	pci_remove_saved_cap(save_state);
 	kfree(save_state);
 }
@@ -308,13 +303,11 @@ static int __pci_save_msix_state(struct pci_dev *dev)
 		return 0;
 
 	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-	if (pos <= 0 || dev->no_msi)
+	if (pos <= 0)
 		return 0;
 
 	/* save the capability */
 	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSIX_FLAGS_ENABLE))
-		return 0;
 	save_state = kzalloc(sizeof(struct pci_cap_saved_state) + sizeof(u16),
 		GFP_KERNEL);
 	if (!save_state) {
@@ -376,6 +369,8 @@ static void __pci_restore_msix_state(struct pci_dev *dev)
 		return;
 
 	/* route the table */
+	pci_intx(dev, 0);		/* disable intx */
+	msix_set_enable(dev, 0);
 	irq = head = dev->first_msi_irq;
 	while (head != tail) {
 		entry = get_irq_msi(irq);
@@ -386,7 +381,6 @@ static void __pci_restore_msix_state(struct pci_dev *dev)
 	}
 
 	pci_write_config_word(dev, msi_control_reg(pos), save);
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSIX);
 }
 
 void pci_restore_msi_state(struct pci_dev *dev)
@@ -411,6 +405,8 @@ static int msi_capability_init(struct pci_dev *dev)
 	int pos, irq;
 	u16 control;
 
+	msi_set_enable(dev, 0);	/* Ensure msi is disabled as I set it up */
+
    	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
 	pci_read_config_word(dev, msi_control_reg(pos), &control);
 	/* MSI Entry Initialization */
@@ -454,7 +450,9 @@ static int msi_capability_init(struct pci_dev *dev)
 	set_irq_msi(irq, entry);
 
 	/* Set MSI enabled bits	 */
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSI);
+	pci_intx(dev, 0);		/* disable intx */
+	msi_set_enable(dev, 1);
+	dev->msi_enabled = 1;
 
 	dev->irq = irq;
 	return 0;
@@ -481,6 +479,8 @@ 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);
 	/* Request & Map MSI-X table region */
  	pci_read_config_word(dev, msi_control_reg(pos), &control);
@@ -549,7 +549,9 @@ static int msix_capability_init(struct pci_dev *dev,
 	}
 	dev->first_msi_irq = entries[0].vector;
 	/* Set MSI-X enabled bits */
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSIX);
+	pci_intx(dev, 0);		/* disable intx */
+	msix_set_enable(dev, 1);
+	dev->msix_enabled = 1;
 
 	return 0;
 }
@@ -611,12 +613,11 @@ int pci_enable_msi(struct pci_dev* dev)
 	WARN_ON(!!dev->msi_enabled);
 
 	/* Check whether driver already requested for MSI-X irqs */
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-	if (pos > 0 && dev->msix_enabled) {
-			printk(KERN_INFO "PCI: %s: Can't enable MSI.  "
-			       "Device already has MSI-X enabled\n",
-			       pci_name(dev));
-			return -EINVAL;
+	if (dev->msix_enabled) {
+		printk(KERN_INFO "PCI: %s: Can't enable MSI.  "
+			"Device already has MSI-X enabled\n",
+			pci_name(dev));
+		return -EINVAL;
 	}
 	status = msi_capability_init(dev);
 	return status;
@@ -625,8 +626,7 @@ int pci_enable_msi(struct pci_dev* dev)
 void pci_disable_msi(struct pci_dev* dev)
 {
 	struct msi_desc *entry;
-	int pos, default_irq;
-	u16 control;
+	int default_irq;
 
 	if (!pci_msi_enable)
 		return;
@@ -636,16 +636,9 @@ void pci_disable_msi(struct pci_dev* dev)
 	if (!dev->msi_enabled)
 		return;
 
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
-	if (!pos)
-		return;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSI_FLAGS_ENABLE))
-		return;
-
-
-	disable_msi_mode(dev, pos, PCI_CAP_ID_MSI);
+	msi_set_enable(dev, 0);
+	pci_intx(dev, 1);		/* enable intx */
+	dev->msi_enabled = 0;
 
 	entry = get_irq_msi(dev->first_msi_irq);
 	if (!entry || !entry->dev || entry->msi_attrib.type != PCI_CAP_ID_MSI) {
@@ -746,8 +739,7 @@ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec)
 	WARN_ON(!!dev->msix_enabled);
 
 	/* Check whether driver already requested for MSI irq */
-   	if (pci_find_capability(dev, PCI_CAP_ID_MSI) > 0 &&
-		dev->msi_enabled) {
+   	if (dev->msi_enabled) {
 		printk(KERN_INFO "PCI: %s: Can't enable MSI-X.  "
 		       "Device already has an MSI irq assigned\n",
 		       pci_name(dev));
@@ -760,8 +752,6 @@ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec)
 void pci_disable_msix(struct pci_dev* dev)
 {
 	int irq, head, tail = 0, warning = 0;
-	int pos;
-	u16 control;
 
 	if (!pci_msi_enable)
 		return;
@@ -771,15 +761,9 @@ void pci_disable_msix(struct pci_dev* dev)
 	if (!dev->msix_enabled)
 		return;
 
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-	if (!pos)
-		return;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSIX_FLAGS_ENABLE))
-		return;
-
-	disable_msi_mode(dev, pos, PCI_CAP_ID_MSIX);
+	msix_set_enable(dev, 0);
+	pci_intx(dev, 1);		/* enable intx */
+	dev->msix_enabled = 0;
 
 	irq = head = dev->first_msi_irq;
 	while (head != tail) {
-- 
1.5.0.g53756

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