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Subject[PATCH V4 1/3] x86/Hyper-V: Set x2apic destination mode to physical when x2apic is available
Date
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.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
---
Change since v2:
- Fix compile error due to x2apic_phys
- Fix comment indent
Change since v1:
- Remove redundant extern for x2apic_phys
---
arch/x86/kernel/cpu/mshyperv.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index e81a2db..0c29e4e 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -328,6 +328,16 @@ 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_X86_X2APIC) && x2apic_supported())
+ x2apic_phys = 1;
+
#endif
}

--
2.7.4
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