xen/pci: Use APIC directly when APIC virtualization hardware is available

[pandora-kernel.git] / arch / x86 / pci / xen.c

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 1370716..37914ef 100644 (file)
--- 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)
@@ -434,6 +436,20 @@ int __init pci_xen_init(void)
 #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;
 }