Drivers: hv: Base autoeoi enablement based on hypervisor hints

Don't enable auto-eoi if the hypervisor recommends otherwise. This will
enable vAPIC functionality if available.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/include/uapi/asm/hyperv.h

@@ -147,6 +147,11 @@
  */
 #define HV_X64_RELAXED_TIMING_RECOMMENDED	(1 << 5)
 
+/*
+ * Virtual APIC support
+ */
+#define HV_X64_DEPRECATING_AEOI_RECOMMENDED	(1 << 9)
+
 /*
  * Crash notification flag.
  */

drivers/hv/hv.c

@@ -254,7 +254,10 @@ int hv_synic_init(unsigned int cpu)
 	shared_sint.as_uint64 = 0;
 	shared_sint.vector = HYPERVISOR_CALLBACK_VECTOR;
 	shared_sint.masked = false;
-	shared_sint.auto_eoi = true;
+	if (ms_hyperv.hints & HV_X64_DEPRECATING_AEOI_RECOMMENDED)
+		shared_sint.auto_eoi = false;
+	else
+		shared_sint.auto_eoi = true;
 
 	hv_set_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
 			    shared_sint.as_uint64);