[PATCH 1/3] x86/Hyper-V: Set x2apic destination mode to physical when x2apic is available

[lantianyu1986@gmail.com]

From: Lan Tianyu <Tianyu.Lan@microsoft.com>

Hyper-V doesn't provide irq remapping for IO-APIC. To enable x2apic,
set x2apic destination mode to physcial mode when x2apic is available
and Hyper-V IOMMU driver makes sure cpus assigned with IO-APIC irqs have
8-bit APIC id.

Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index e81a2db..9d62f33 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -36,6 +36,8 @@
 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
 
+extern int x2apic_phys;
+
 #if IS_ENABLED(CONFIG_HYPERV)
 static void (*vmbus_handler)(void);
 static void (*hv_stimer0_handler)(void);
@@ -328,6 +330,18 @@ static void __init ms_hyperv_init_platform(void)
 # ifdef CONFIG_SMP
 	smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
 # endif
+
+/*
+ * Hyper-V doesn't provide irq remapping for IO-APIC. To enable x2apic,
+ * set x2apic destination mode to physcial mode when x2apic is available
+ * and Hyper-V IOMMU driver makes sure cpus assigned with IO-APIC irqs
+ * have 8-bit APIC id.
+ */
+# if IS_ENABLED(CONFIG_HYPERV_IOMMU)
+	if (x2apic_supported())
+		x2apic_phys = 1;
+# endif
+
 #endif
 }
 
-- 
2.7.4