[PATCH] x86/acrn: Allow ACRN guest to use X2APIC mode

From: Shuo Liu
Date: Thu Aug 06 2020 - 13:22:43 EST

The ACRN Hypervisor did not support x2APIC and thus x2APIC support was
disabled by always returning false when VM checked for x2APIC support.

ACRN received full support of x2APIC and exports the capability through
CPUID feature bits.

Let VM decide if it needs to switch to x2APIC mode according to CPUID

Originally-by: Yakui Zhao <yakui.zhao@xxxxxxxxx>
Signed-off-by: Shuo Liu <shuo.a.liu@xxxxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Fengwei Yin <fengwei.yin@xxxxxxxxx>
Cc: Zhi Wang <zhi.a.wang@xxxxxxxxx>
Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
Cc: Yu Wang <yu1.wang@xxxxxxxxx>
Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
arch/x86/kernel/cpu/acrn.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index 1da9b1c9a2db..3b08cdfc6514 100644
--- a/arch/x86/kernel/cpu/acrn.c
+++ b/arch/x86/kernel/cpu/acrn.c
@@ -11,6 +11,7 @@

#include <linux/interrupt.h>
#include <asm/apic.h>
+#include <asm/cpufeatures.h>
#include <asm/desc.h>
#include <asm/hypervisor.h>
#include <asm/idtentry.h>
@@ -29,12 +30,7 @@ static void __init acrn_init_platform(void)

static bool acrn_x2apic_available(void)
- /*
- * x2apic is not supported for now. Future enablement will have to check
- * X86_FEATURE_X2APIC to determine whether x2apic is supported in the
- * guest.
- */
- return false;
+ return boot_cpu_has(X86_FEATURE_X2APIC);

static void (*acrn_intr_handler)(void);

base-commit: 48778464bb7d346b47157d21ffde2af6b2d39110