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

Lan Tianyu · joergroedel · commit 84fdfafab849 · 2019-02-28T11:12:16.000+01:00
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 &lt;tglx@linutronix.de&gt;
Reviewed-by: Michael Kelley &lt;mikelley@microsoft.com&gt;
Signed-off-by: Lan Tianyu &lt;Tianyu.Lan@microsoft.com&gt;
Signed-off-by: Joerg Roedel &lt;jroedel@suse.de&gt;
diff --git 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
 }
 
