[PATCH] PCI/MSI: Handle the NOMASK flag correctly for all PCI/MSI backends

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

The conversion of the XEN specific global variable pci_msi_ignore_mask to a
MSI domain flag, missed the facts that:

    1) Legacy architectures do not provide a interrupt domain
    2) Parent MSI domains do not necessarily have a domain info attached
   
Both cases result in an unconditional NULL pointer dereference.

Cure this by using the existing pci_msi_domain_supports() helper, which
handles all possible cases correctly.

Fixes: c3164d2e0d18 ("PCI/MSI: Convert pci_msi_ignore_mask to per MSI domain 
flag")
Reported-by: Daniel Gomez <da.gomez@xxxxxxxxxx>
Reported-by: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Tested-by: Borislav Petkov <bp@xxxxxxxxx>
Tested-by: Daniel Gomez <da.gomez@xxxxxxxxxx>
---
 drivers/pci/msi/msi.c |   18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)



--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -285,8 +285,6 @@ static void pci_msi_set_enable(struct pc
 static int msi_setup_msi_desc(struct pci_dev *dev, int nvec,
                              struct irq_affinity_desc *masks)
 {
-       const struct irq_domain *d = dev_get_msi_domain(&dev->dev);
-       const struct msi_domain_info *info = d->host_data;
        struct msi_desc desc;
        u16 control;
 
@@ -297,7 +295,7 @@ static int msi_setup_msi_desc(struct pci
        /* Lies, damned lies, and MSIs */
        if (dev->dev_flags & PCI_DEV_FLAGS_HAS_MSI_MASKING)
                control |= PCI_MSI_FLAGS_MASKBIT;
-       if (info->flags & MSI_FLAG_NO_MASK)
+       if (pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY))
                control &= ~PCI_MSI_FLAGS_MASKBIT;
 
        desc.nvec_used                  = nvec;
@@ -604,20 +602,18 @@ static void __iomem *msix_map_region(str
  */
 void msix_prepare_msi_desc(struct pci_dev *dev, struct msi_desc *desc)
 {
-       const struct irq_domain *d = dev_get_msi_domain(&dev->dev);
-       const struct msi_domain_info *info = d->host_data;
-
        desc->nvec_used                         = 1;
        desc->pci.msi_attrib.is_msix            = 1;
        desc->pci.msi_attrib.is_64              = 1;
        desc->pci.msi_attrib.default_irq        = dev->irq;
        desc->pci.mask_base                     = dev->msix_base;
-       desc->pci.msi_attrib.can_mask           = !(info->flags & 
MSI_FLAG_NO_MASK) &&
-                                                 
!desc->pci.msi_attrib.is_virtual;
 
-       if (desc->pci.msi_attrib.can_mask) {
+
+       if (!pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY) &&
+           !desc->pci.msi_attrib.is_virtual) {
                void __iomem *addr = pci_msix_desc_addr(desc);
 
+               desc->pci.msi_attrib.can_mask = 1;
                desc->pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
        }
 }
@@ -715,8 +711,6 @@ static int msix_setup_interrupts(struct
 static int msix_capability_init(struct pci_dev *dev, struct msix_entry 
*entries,
                                int nvec, struct irq_affinity *affd)
 {
-       const struct irq_domain *d = dev_get_msi_domain(&dev->dev);
-       const struct msi_domain_info *info = d->host_data;
        int ret, tsize;
        u16 control;
 
@@ -747,7 +741,7 @@ static int msix_capability_init(struct p
        /* Disable INTX */
        pci_intx_for_msi(dev, 0);
 
-       if (!(info->flags & MSI_FLAG_NO_MASK)) {
+       if (!pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY)) {
                /*
                 * Ensure that all table entries are masked to prevent
                 * stale entries from firing in a crash kernel.