[PATCH] PCI/MSI: Move non-mask check back into low level accessors

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

The recent rework of PCI/MSI[X] masking moved the non-mask checks from the
low level accessors into the higher level mask/unmask functions.

This missed the fact that these accessors can be invoked from other places
as well. The missing checks break XEN-PV which sets pci_msi_ignore_mask and
also violates the virtual MSIX and the msi_attrib.maskbit protections.

Instead of sprinkling checks all over the place, lift them back into the
low level accessor functions. To avoid checking three different conditions
combine them into one property of msi_desc::msi_attrib.

Reported-by: Josef Johansson <josef@xxxxxxxxxxx>
Fixes: fcacdfbef5a1 ("PCI/MSI: Provide a new set of mask and unmask functions")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jason Andryuk <jandryuk@xxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Bjorn Helgaas <helgaas@xxxxxxxxxx>
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
---
 drivers/pci/msi.c   |   26 ++++++++++++++------------
 include/linux/msi.h |    2 +-
 2 files changed, 15 insertions(+), 13 deletions(-)

--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -148,6 +148,9 @@ static noinline void pci_msi_update_mask
        raw_spinlock_t *lock = &desc->dev->msi_lock;
        unsigned long flags;
 
+       if (!desc->msi_attrib.can_mask)
+               return;
+
        raw_spin_lock_irqsave(lock, flags);
        desc->msi_mask &= ~clear;
        desc->msi_mask |= set;
@@ -181,7 +184,8 @@ static void pci_msix_write_vector_ctrl(s
 {
        void __iomem *desc_addr = pci_msix_desc_addr(desc);
 
-       writel(ctrl, desc_addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
+       if (desc->msi_attrib.can_mask)
+               writel(ctrl, desc_addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
 }
 
 static inline void pci_msix_mask(struct msi_desc *desc)
@@ -200,23 +204,17 @@ static inline void pci_msix_unmask(struc
 
 static void __pci_msi_mask_desc(struct msi_desc *desc, u32 mask)
 {
-       if (pci_msi_ignore_mask || desc->msi_attrib.is_virtual)
-               return;
-
        if (desc->msi_attrib.is_msix)
                pci_msix_mask(desc);
-       else if (desc->msi_attrib.maskbit)
+       else
                pci_msi_mask(desc, mask);
 }
 
 static void __pci_msi_unmask_desc(struct msi_desc *desc, u32 mask)
 {
-       if (pci_msi_ignore_mask || desc->msi_attrib.is_virtual)
-               return;
-
        if (desc->msi_attrib.is_msix)
                pci_msix_unmask(desc);
-       else if (desc->msi_attrib.maskbit)
+       else
                pci_msi_unmask(desc, mask);
 }
 
@@ -484,7 +482,8 @@ msi_setup_entry(struct pci_dev *dev, int
        entry->msi_attrib.is_64         = !!(control & PCI_MSI_FLAGS_64BIT);
        entry->msi_attrib.is_virtual    = 0;
        entry->msi_attrib.entry_nr      = 0;
-       entry->msi_attrib.maskbit       = !!(control & PCI_MSI_FLAGS_MASKBIT);
+       entry->msi_attrib.can_mask      = !pci_msi_ignore_mask &&
+                                         !!(control & PCI_MSI_FLAGS_MASKBIT);
        entry->msi_attrib.default_irq   = dev->irq;     /* Save IOAPIC IRQ */
        entry->msi_attrib.multi_cap     = (control & PCI_MSI_FLAGS_QMASK) >> 1;
        entry->msi_attrib.multiple      = ilog2(__roundup_pow_of_two(nvec));
@@ -495,7 +494,7 @@ msi_setup_entry(struct pci_dev *dev, int
                entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_32;
 
        /* Save the initial mask status */
-       if (entry->msi_attrib.maskbit)
+       if (entry->msi_attrib.can_mask)
                pci_read_config_dword(dev, entry->mask_pos, &entry->msi_mask);
 
 out:
@@ -638,10 +637,13 @@ static int msix_setup_entries(struct pci
                entry->msi_attrib.is_virtual =
                        entry->msi_attrib.entry_nr >= vec_count;
 
+               entry->msi_attrib.can_mask      = !pci_msi_ignore_mask &&
+                                                 !entry->msi_attrib.is_virtual;
+
                entry->msi_attrib.default_irq   = dev->irq;
                entry->mask_base                = base;
 
-               if (!entry->msi_attrib.is_virtual) {
+               if (!entry->msi_attrib.can_mask) {
                        addr = pci_msix_desc_addr(entry);
                        entry->msix_ctrl = readl(addr + 
PCI_MSIX_ENTRY_VECTOR_CTRL);
                }
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -148,7 +148,7 @@ struct msi_desc {
                                u8      is_msix         : 1;
                                u8      multiple        : 3;
                                u8      multi_cap       : 3;
-                               u8      maskbit         : 1;
+                               u8      can_mask        : 1;
                                u8      is_64           : 1;
                                u8      is_virtual      : 1;
                                u16     entry_nr;