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Subject: [PATCH V3 1/3] x86/Hyper-V: Set x2apic destination mode to physical when x2apic is available
Date:   Thu,  7 Feb 2019 23:33:47 +0800
Message-Id: <1549553629-8414-2-git-send-email-Tianyu.Lan@microsoft.com>
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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>
---
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