PCI/MSI: Disable MSI at enumeration even if kernel doesn't support MSI

If we enable MSI, then kexec a new kernel, the new kernel may receive MSIs
it is not prepared for.  Commit d5dea7d95c48 ("PCI: msi: Disable msi
interrupts when we initialize a pci device") prevents this, but only if the
new kernel is built with CONFIG_PCI_MSI=y.

Move the "disable MSI" functionality from drivers/pci/msi.c to a new
pci_msi_setup_pci_dev() in drivers/pci/probe.c so we can disable MSIs when
we enumerate devices even if the kernel doesn't include full MSI support.

[bhelgaas: changelog, disable MSIs in pci_setup_device(), put
pci_msi_setup_pci_dev() at its final destination]
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 6675a7a1b9fc..a9c5e63049a5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1085,6 +1085,22 @@ int pci_cfg_space_size(struct pci_dev *dev)
 
 #define LEGACY_IO_RESOURCE      (IORESOURCE_IO | IORESOURCE_PCI_FIXED)
 
+static void pci_msi_setup_pci_dev(struct pci_dev *dev)
+{
+        /*
+         * Disable the MSI hardware to avoid screaming interrupts
+         * during boot.  This is the power on reset default so
+         * usually this should be a noop.
+         */
+        dev->msi_cap = pci_find_capability(dev, PCI_CAP_ID_MSI);
+        if (dev->msi_cap)
+                pci_msi_set_enable(dev, 0);
+
+        dev->msix_cap = pci_find_capability(dev, PCI_CAP_ID_MSIX);
+        if (dev->msix_cap)
+                pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
+}
+
 /**
  * pci_setup_device - fill in class and map information of a device
  * @dev: the device structure to fill
@@ -1140,6 +1156,8 @@ int pci_setup_device(struct pci_dev *dev)
         /* "Unknown power state" */
         dev->current_state = PCI_UNKNOWN;
 
+        pci_msi_setup_pci_dev(dev);
+
         /* Early fixups, before probing the BARs */
         pci_fixup_device(pci_fixup_early, dev);
         /* device class may be changed after fixup */