PCI: Fail MSI-X mappings if there's no space assigned to MSI-X BAR

Unlike MSI, which is configured via registers in the MSI capability in
Configuration Space, MSI-X is configured via tables in Memory Space.
These MSI-X tables are mapped by a device BAR, and if no Memory Space
has been assigned to the BAR, MSI-X cannot be used.

Fail MSI-X setup if no space has been assigned for the BAR.

Previously, we ioremapped the MSI-X table even if the resource hadn't been
assigned.  In this case, the resource address is undefined (and is often
zero), which may lead to warnings or oopses in this path:

  pci_enable_msix
    msix_capability_init
      msix_map_region
        ioremap_nocache

The PCI core sets resource flags to zero when it can't assign space for the
resource (see reset_resource()).  There are also some cases where it sets
the IORESOURCE_UNSET flag, e.g., pci_reassigndev_resource_alignment(),
pci_assign_resource(), etc.  So we must check for both cases.

[bhelgaas: changelog]
Reported-by: Zhang Jukuo <zhangjukuo@huawei.com>
Tested-by: Zhang Jukuo <zhangjukuo@huawei.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index c489ef2c1a39..34fc4189ebf0 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -298,12 +298,16 @@ static int xen_initdom_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
                         map_irq.entry_nr = nvec;
                 } else if (type == PCI_CAP_ID_MSIX) {
                         int pos;
+                        unsigned long flags;
                         u32 table_offset, bir;
 
                         pos = dev->msix_cap;
                         pci_read_config_dword(dev, pos + PCI_MSIX_TABLE,
                                               &table_offset);
                         bir = (u8)(table_offset & PCI_MSIX_TABLE_BIR);
+                        flags = pci_resource_flags(dev, bir);
+                        if (!flags || (flags & IORESOURCE_UNSET))
+                                return -EINVAL;
 
                         map_irq.table_base = pci_resource_start(dev, bir);
                         map_irq.entry_nr = msidesc->msi_attrib.entry_nr;