x86/acrn: Allow ACRN guest to use X2APIC mode

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
features.

Originally-by: Yakui Zhao <yakui.zhao@intel.com>
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/20200806113802.9325-1-shuo.a.liu@intel.com

diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index 1da9b1c9a2dbf92049bbf54c76f74753e73acf98..3b08cdfc6514c04d85d8607eeebb25adb262e3bc 100644 (file)
--- 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);