[PATCH] msi: Safer state caching.

There are two ways pci_save_state and pci_restore_state are used.  As
helper functions during suspend/resume, and as helper functions around
a hardware reset event.  When used as helper functions around a hardware
reset event there is no reason to believe the calls will be paired, nor
is there a good reason to believe that if we restore the msi state from
before the reset that it will match the current msi state.  Since arch
code may change the msi message without going through the driver, drivers
currently do not have enough information to even know when to call
pci_save_state to ensure they will have msi state in sync with the other
kernel irq reception data structures.

It turns out the solution is straight forward, cache the state in the
existing msi data structures (not the magic pci saved things) and
have the msi code update the cached state each time we write to the hardware.
This means we never need to read the hardware to figure out what the hardware
state should be.

By modifying the caching in this manner we get to remove our save_state
routines and only need to provide restore_state routines.

The only fields that were at all tricky to regenerate were the msi and msi-x
control registers and the way we regenerate them currently is a bit dependent
upon assumptions on how we use the allow msi registers to be configured and used
making the code a little bit brittle.  If we ever change what cases we allow
or how we configure the msi bits we can address the fragility then.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 25 insertions, 129 deletions

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 01869b1782e4..ad33e0159514 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -100,6 +100,7 @@ static void msi_set_mask_bit(unsigned int irq, int flag)
                 BUG();
                 break;
         }
+        entry->msi_attrib.masked = !!flag;
 }
 
 void read_msi_msg(unsigned int irq, struct msi_msg *msg)
@@ -179,6 +180,7 @@ void write_msi_msg(unsigned int irq, struct msi_msg *msg)
         default:
                 BUG();
         }
+        entry->msg = *msg;
 }
 
 void mask_msi_irq(unsigned int irq)
@@ -225,164 +227,60 @@ static struct msi_desc* alloc_msi_entry(void)
 }
 
 #ifdef CONFIG_PM
-static int __pci_save_msi_state(struct pci_dev *dev)
-{
-        int pos, i = 0;
-        u16 control;
-        struct pci_cap_saved_state *save_state;
-        u32 *cap;
-
-        if (!dev->msi_enabled)
-                return 0;
-
-        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,
-                GFP_KERNEL);
-        if (!save_state) {
-                printk(KERN_ERR "Out of memory in pci_save_msi_state\n");
-                return -ENOMEM;
-        }
-        cap = &save_state->data[0];
-
-        pci_read_config_dword(dev, pos, &cap[i++]);
-        control = cap[0] >> 16;
-        pci_read_config_dword(dev, pos + PCI_MSI_ADDRESS_LO, &cap[i++]);
-        if (control & PCI_MSI_FLAGS_64BIT) {
-                pci_read_config_dword(dev, pos + PCI_MSI_ADDRESS_HI, &cap[i++]);
-                pci_read_config_dword(dev, pos + PCI_MSI_DATA_64, &cap[i++]);
-        } else
-                pci_read_config_dword(dev, pos + PCI_MSI_DATA_32, &cap[i++]);
-        if (control & PCI_MSI_FLAGS_MASKBIT)
-                pci_read_config_dword(dev, pos + PCI_MSI_MASK_BIT, &cap[i++]);
-        save_state->cap_nr = PCI_CAP_ID_MSI;
-        pci_add_saved_cap(dev, save_state);
-        return 0;
-}
-
 static void __pci_restore_msi_state(struct pci_dev *dev)
 {
-        int i = 0, pos;
+        int pos;
         u16 control;
-        struct pci_cap_saved_state *save_state;
-        u32 *cap;
+        struct msi_desc *entry;
 
         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];
+        entry = get_irq_msi(dev->irq);
+        pos = entry->msi_attrib.pos;
 
         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++]);
-                pci_write_config_dword(dev, pos + PCI_MSI_DATA_64, cap[i++]);
-        } else
-                pci_write_config_dword(dev, pos + PCI_MSI_DATA_32, cap[i++]);
-        if (control & PCI_MSI_FLAGS_MASKBIT)
-                pci_write_config_dword(dev, pos + PCI_MSI_MASK_BIT, cap[i++]);
+        write_msi_msg(dev->irq, &entry->msg);
+        if (entry->msi_attrib.maskbit)
+                msi_set_mask_bit(dev->irq, entry->msi_attrib.masked);
+
+        pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
+        control &= ~(PCI_MSI_FLAGS_QSIZE | PCI_MSI_FLAGS_ENABLE);
+        if (entry->msi_attrib.maskbit || !entry->msi_attrib.masked)
+                control |= PCI_MSI_FLAGS_ENABLE;
         pci_write_config_word(dev, pos + PCI_MSI_FLAGS, control);
-        pci_remove_saved_cap(save_state);
-        kfree(save_state);
-}
-
-static int __pci_save_msix_state(struct pci_dev *dev)
-{
-        int pos;
-        int irq, head, tail = 0;
-        u16 control;
-        struct pci_cap_saved_state *save_state;
-
-        if (!dev->msix_enabled)
-                return 0;
-
-        pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-        if (pos <= 0)
-                return 0;
-
-        /* save the capability */
-        pci_read_config_word(dev, msi_control_reg(pos), &control);
-        save_state = kzalloc(sizeof(struct pci_cap_saved_state) + sizeof(u16),
-                GFP_KERNEL);
-        if (!save_state) {
-                printk(KERN_ERR "Out of memory in pci_save_msix_state\n");
-                return -ENOMEM;
-        }
-        *((u16 *)&save_state->data[0]) = control;
-
-        /* save the table */
-        irq = head = dev->first_msi_irq;
-        while (head != tail) {
-                struct msi_desc *entry;
-
-                entry = get_irq_msi(irq);
-                read_msi_msg(irq, &entry->msg_save);
-
-                tail = entry->link.tail;
-                irq = tail;
-        }
-
-        save_state->cap_nr = PCI_CAP_ID_MSIX;
-        pci_add_saved_cap(dev, save_state);
-        return 0;
-}
-
-int pci_save_msi_state(struct pci_dev *dev)
-{
-        int rc;
-
-        rc = __pci_save_msi_state(dev);
-        if (rc)
-                return rc;
-
-        rc = __pci_save_msix_state(dev);
-
-        return rc;
 }
 
 static void __pci_restore_msix_state(struct pci_dev *dev)
 {
-        u16 save;
         int pos;
         int irq, head, tail = 0;
         struct msi_desc *entry;
-        struct pci_cap_saved_state *save_state;
+        u16 control;
 
         if (!dev->msix_enabled)
                 return;
 
-        save_state = pci_find_saved_cap(dev, PCI_CAP_ID_MSIX);
-        if (!save_state)
-                return;
-        save = *((u16 *)&save_state->data[0]);
-        pci_remove_saved_cap(save_state);
-        kfree(save_state);
-
-        pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-        if (pos <= 0)
-                return;
-
         /* route the table */
         pci_intx(dev, 0);               /* disable intx */
         msix_set_enable(dev, 0);
         irq = head = dev->first_msi_irq;
+        entry = get_irq_msi(irq);
+        pos = entry->msi_attrib.pos;
         while (head != tail) {
                 entry = get_irq_msi(irq);
-                write_msi_msg(irq, &entry->msg_save);
+                write_msi_msg(irq, &entry->msg);
+                msi_set_mask_bit(irq, entry->msi_attrib.masked);
 
                 tail = entry->link.tail;
                 irq = tail;
         }
 
-        pci_write_config_word(dev, msi_control_reg(pos), save);
+        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);
 }
 
 void pci_restore_msi_state(struct pci_dev *dev)
@@ -420,6 +318,7 @@ static int msi_capability_init(struct pci_dev *dev)
         entry->msi_attrib.is_64 = is_64bit_address(control);
         entry->msi_attrib.entry_nr = 0;
         entry->msi_attrib.maskbit = is_mask_bit_support(control);
+        entry->msi_attrib.masked = 1;
         entry->msi_attrib.default_irq = dev->irq;       /* Save IOAPIC IRQ */
         entry->msi_attrib.pos = pos;
         if (is_mask_bit_support(control)) {
@@ -507,6 +406,7 @@ static int msix_capability_init(struct pci_dev *dev,
                 entry->msi_attrib.is_64 = 1;
                 entry->msi_attrib.entry_nr = j;
                 entry->msi_attrib.maskbit = 1;
+                entry->msi_attrib.masked = 1;
                 entry->msi_attrib.default_irq = dev->irq;
                 entry->msi_attrib.pos = pos;
                 entry->dev = dev;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index a32db0628157..6048c0c637a0 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -638,8 +638,6 @@ pci_save_state(struct pci_dev *dev)
         /* XXX: 100% dword access ok here? */
         for (i = 0; i < 16; i++)
                 pci_read_config_dword(dev, i * 4,&dev->saved_config_space[i]);
-        if ((i = pci_save_msi_state(dev)) != 0)
-                return i;
         if ((i = pci_save_pcie_state(dev)) != 0)
                 return i;
         if ((i = pci_save_pcix_state(dev)) != 0)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index ae7a975995a5..62ea04c8af64 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -52,10 +52,8 @@ static inline void pci_no_msi(void) { }
 #endif
 
 #if defined(CONFIG_PCI_MSI) && defined(CONFIG_PM)
-int pci_save_msi_state(struct pci_dev *dev);
 void pci_restore_msi_state(struct pci_dev *dev);
 #else
-static inline int pci_save_msi_state(struct pci_dev *dev) { return 0; }
 static inline void pci_restore_msi_state(struct pci_dev *dev) {}
 #endif