1 files changed, 29 insertions, 2 deletions

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 1819a91bbb9f..c489ef2c1a39 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -23,6 +23,8 @@
 #include <xen/features.h>
 #include <xen/events.h>
 #include <asm/xen/pci.h>
+#include <asm/xen/cpuid.h>
+#include <asm/apic.h>
 #include <asm/i8259.h>
 
 static int xen_pcifront_enable_irq(struct pci_dev *dev)
@@ -423,6 +425,28 @@ int __init pci_xen_init(void)
         return 0;
 }
 
+#ifdef CONFIG_PCI_MSI
+void __init xen_msi_init(void)
+{
+        if (!disable_apic) {
+                /*
+                 * If hardware supports (x2)APIC virtualization (as indicated
+                 * by hypervisor's leaf 4) then we don't need to use pirqs/
+                 * event channels for MSI handling and instead use regular
+                 * APIC processing
+                 */
+                uint32_t eax = cpuid_eax(xen_cpuid_base() + 4);
+
+                if (((eax & XEN_HVM_CPUID_X2APIC_VIRT) && x2apic_mode) ||
+                    ((eax & XEN_HVM_CPUID_APIC_ACCESS_VIRT) && cpu_has_apic))
+                        return;
+        }
+
+        x86_msi.setup_msi_irqs = xen_hvm_setup_msi_irqs;
+        x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
+}
+#endif
+
 int __init pci_xen_hvm_init(void)
 {
         if (!xen_have_vector_callback || !xen_feature(XENFEAT_hvm_pirqs))
@@ -437,8 +461,11 @@ int __init pci_xen_hvm_init(void)
 #endif
 
 #ifdef CONFIG_PCI_MSI
-        x86_msi.setup_msi_irqs = xen_hvm_setup_msi_irqs;
-        x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
+        /*
+         * We need to wait until after x2apic is initialized
+         * before we can set MSI IRQ ops.
+         */
+        x86_platform.apic_post_init = xen_msi_init;
 #endif
         return 0;
 }