PCI: Add x86_msi.msi_mask_irq() and msix_mask_irq()

Certain platforms do not allow writes in the MSI-X BARs to setup or tear
down vector values.  To combat against the generic code trying to write to
that and either silently being ignored or crashing due to the pagetables
being marked R/O this patch introduces a platform override.

Note that we keep two separate, non-weak, functions default_mask_msi_irqs()
and default_mask_msix_irqs() for the behavior of the arch_mask_msi_irqs()
and arch_mask_msix_irqs(), as the default behavior is needed by x86 PCI
code.

For Xen, which does not allow the guest to write to MSI-X tables - as the
hypervisor is solely responsible for setting the vector values - we
implement two nops.

This fixes a Xen guest crash when passing a PCI device with MSI-X to the
guest.  See the bugzilla for more details.

[bhelgaas: add bugzilla info]
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=64581
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
CC: Zhenzhong Duan <zhenzhong.duan@oracle.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 48e8461057ba..5eee4959785d 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -382,7 +382,14 @@ static void xen_teardown_msi_irq(unsigned int irq)
 {
 	xen_destroy_irq(irq);
 }
-
+static u32 xen_nop_msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
+{
+	return 0;
+}
+static u32 xen_nop_msix_mask_irq(struct msi_desc *desc, u32 flag)
+{
+	return 0;
+}
 #endif
 
 int __init pci_xen_init(void)
@@ -406,6 +413,8 @@ int __init pci_xen_init(void)
 	x86_msi.setup_msi_irqs = xen_setup_msi_irqs;
 	x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
 	x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
+	x86_msi.msi_mask_irq = xen_nop_msi_mask_irq;
+	x86_msi.msix_mask_irq = xen_nop_msix_mask_irq;
 #endif
 	return 0;
 }
@@ -485,6 +494,8 @@ int __init pci_xen_initial_domain(void)
 	x86_msi.setup_msi_irqs = xen_initdom_setup_msi_irqs;
 	x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
 	x86_msi.restore_msi_irqs = xen_initdom_restore_msi_irqs;
+	x86_msi.msi_mask_irq = xen_nop_msi_mask_irq;
+	x86_msi.msix_mask_irq = xen_nop_msix_mask_irq;
 #endif
 	xen_setup_acpi_sci();
 	__acpi_register_gsi = acpi_register_gsi_xen;