hv: vmbus_drv: detect hyperv through x86_hyper

There are two reasons we need to use x86_hyper instead of
query_hypervisor_presence():

- Not only hyperv but also other hypervisors such as kvm would set
  X86_FEATURE_HYTPERVISOR, so query_hypervisor_presence() will return true even
  in kvm. This may cause extra delay of 5 seconds before failing the probing in
  kvm guest.
- The hypervisor has been detected in init_hypervisor(), so no need to do the
  work again.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 23 deletions

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index f40dd57bbec1..8e1a9ec53003 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -34,6 +34,7 @@
 #include <linux/completion.h>
 #include <linux/hyperv.h>
 #include <asm/hyperv.h>
+#include <asm/hypervisor.h>
 #include "hyperv_vmbus.h"
 
 
@@ -719,33 +720,11 @@ static struct acpi_driver vmbus_acpi_driver = {
         },
 };
 
-/*
- * query_hypervisor_presence
- * - Query the cpuid for presence of windows hypervisor
- */
-static int query_hypervisor_presence(void)
-{
-        unsigned int eax;
-        unsigned int ebx;
-        unsigned int ecx;
-        unsigned int edx;
-        unsigned int op;
-
-        eax = 0;
-        ebx = 0;
-        ecx = 0;
-        edx = 0;
-        op = HVCPUID_VERSION_FEATURES;
-        cpuid(op, &eax, &ebx, &ecx, &edx);
-
-        return ecx & HV_PRESENT_BIT;
-}
-
 static int __init hv_acpi_init(void)
 {
         int ret, t;
 
-        if (!query_hypervisor_presence())
+        if (x86_hyper != &x86_hyper_ms_hyperv)
                 return -ENODEV;
 
         init_completion(&probe_event);