[PATCH v2] xen: HVM X2APIC support

[Sheng Yang <sheng@linux.intel.com>]

This patch is similiar to Gleb Natapov's patch for KVM, which enable the
hypervisor to emulate x2apic feature for the guest. By this way, the emulation
of lapic would be simpler with x2apic interface(MSR), and faster.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 arch/x86/include/asm/xen/hypervisor.h |   35 +++++++++++++++++++++++++++++++++
 arch/x86/kernel/apic/apic.c           |    4 ++-
 arch/x86/xen/enlighten.c              |   30 ++++++++++-----------------
 3 files changed, 49 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 396ff4c..bc5b804 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -37,4 +37,39 @@
 extern struct shared_info *HYPERVISOR_shared_info;
 extern struct start_info *xen_start_info;
 
+#include <asm/processor.h>
+
+static inline uint32_t xen_cpuid_base(void)
+{
+	uint32_t base, eax, ebx, ecx, edx;
+	char signature[13];
+
+	for (base = 0x40000000; base < 0x40010000; base += 0x100) {
+		cpuid(base, &eax, &ebx, &ecx, &edx);
+		*(uint32_t *)(signature + 0) = ebx;
+		*(uint32_t *)(signature + 4) = ecx;
+		*(uint32_t *)(signature + 8) = edx;
+		signature[12] = 0;
+
+		if (!strcmp("XenVMMXenVMM", signature) && ((eax - base) >= 2))
+			return base;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_XEN
+extern bool xen_hvm_need_lapic(void);
+
+static inline bool xen_para_available(void)
+{
+	return xen_hvm_need_lapic();
+}
+#else
+static inline bool xen_para_available(void)
+{
+	return (xen_cpuid_base() != 0);
+}
+#endif
+
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 3f838d5..1b68221 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -52,6 +52,7 @@
 #include <asm/mce.h>
 #include <asm/kvm_para.h>
 #include <asm/tsc.h>
+#include <asm/xen/hypervisor.h>
 
 unsigned int num_processors;
 
@@ -1476,7 +1477,8 @@ void __init enable_IR_x2apic(void)
 		/* IR is required if there is APIC ID > 255 even when running
 		 * under KVM
 		 */
-		if (max_physical_apicid > 255 || !kvm_para_available())
+		if (max_physical_apicid > 255 ||
+		    (!kvm_para_available() && !xen_para_available()))
 			goto nox2apic;
 		/*
 		 * without IR all CPUs can be addressed by IOAPIC/MSI
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 235c0f4..7ef1645 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1245,25 +1245,6 @@ asmlinkage void __init xen_start_kernel(void)
 #endif
 }
 
-static uint32_t xen_cpuid_base(void)
-{
-	uint32_t base, eax, ebx, ecx, edx;
-	char signature[13];
-
-	for (base = 0x40000000; base < 0x40010000; base += 0x100) {
-		cpuid(base, &eax, &ebx, &ecx, &edx);
-		*(uint32_t *)(signature + 0) = ebx;
-		*(uint32_t *)(signature + 4) = ecx;
-		*(uint32_t *)(signature + 8) = edx;
-		signature[12] = 0;
-
-		if (!strcmp("XenVMMXenVMM", signature) && ((eax - base) >= 2))
-			return base;
-	}
-
-	return 0;
-}
-
 static int init_hvm_pv_info(int *major, int *minor)
 {
 	uint32_t eax, ebx, ecx, edx, pages, msr, base;
@@ -1373,6 +1354,17 @@ static bool __init xen_hvm_platform(void)
 	return true;
 }
 
+bool xen_hvm_need_lapic(void)
+{
+	if (xen_pv_domain())
+		return false;
+	if (xen_hvm_domain() &&
+	   (xen_feature(XENFEAT_hvm_pirqs) || xen_have_vector_callback))
+		return false;
+	return (xen_cpuid_base() != 0);
+}
+EXPORT_SYMBOL_GPL(xen_hvm_need_lapic);
+
 const __refconst struct hypervisor_x86 x86_hyper_xen_hvm = {
 	.name			= "Xen HVM",
 	.detect			= xen_hvm_platform,
-- 
1.7.0.1