x86/Hyper-V: Set x2apic destination mode to physical when x2apic is available

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.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index e81a2db42df7..3fa238a137d2 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -328,6 +328,18 @@ 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.
+         */
+# ifdef CONFIG_X86_X2APIC
+        if (x2apic_supported())
+                x2apic_phys = 1;
+# endif
+
 #endif
 }