6 files changed, 19 insertions, 1 deletions

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 10d0596433f8..c759b3cca663 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -19,6 +19,12 @@ static inline int paravirt_enabled(void)
         return pv_info.paravirt_enabled;
 }
 
+static inline int paravirt_has_feature(unsigned int feature)
+{
+        WARN_ON_ONCE(!pv_info.paravirt_enabled);
+        return (pv_info.features & feature);
+}
+
 static inline void load_sp0(struct tss_struct *tss,
                              struct thread_struct *thread)
 {
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 31247b5bff7c..3d44191185f8 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -70,9 +70,14 @@ struct pv_info {
 #endif
 
         int paravirt_enabled;
+        unsigned int features;    /* valid only if paravirt_enabled is set */
         const char *name;
 };
 
+#define paravirt_has(x) paravirt_has_feature(PV_SUPPORTED_##x)
+/* Supported features */
+#define PV_SUPPORTED_RTC        (1<<0)
+
 struct pv_init_ops {
         /*
          * Patch may replace one of the defined code sequences with
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 67522256c7ff..2d5a50cb61a2 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -472,6 +472,7 @@ static inline unsigned long current_top_of_stack(void)
 #else
 #define __cpuid                 native_cpuid
 #define paravirt_enabled()      0
+#define paravirt_has(x)         0
 
 static inline void load_sp0(struct tss_struct *tss,
                             struct thread_struct *thread)
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index cd9685235df9..4af8d063fb36 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -200,6 +200,9 @@ static __init int add_rtc_cmos(void)
         }
 #endif
 
+        if (paravirt_enabled() && !paravirt_has(RTC))
+                return -ENODEV;
+
         platform_device_register(&rtc_device);
         dev_info(&rtc_device.dev,
                  "registered platform RTC device (no PNP device found)\n");
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index a0d09f6c6533..a43b2eafc466 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1414,6 +1414,7 @@ __init void lguest_init(void)
         pv_info.kernel_rpl = 1;
         /* Everyone except Xen runs with this set. */
         pv_info.shared_kernel_pmd = 1;
+        pv_info.features = 0;
 
         /*
          * We set up all the lguest overrides for sensitive operations.  These
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index d315151411e5..b7de78bdc09c 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1192,7 +1192,7 @@ static const struct pv_info xen_info __initconst = {
 #ifdef CONFIG_X86_64
         .extra_user_64bit_cs = FLAT_USER_CS64,
 #endif
-
+        .features = 0,
         .name = "Xen",
 };
 
@@ -1535,6 +1535,8 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
         /* Install Xen paravirt ops */
         pv_info = xen_info;
+        if (xen_initial_domain())
+                pv_info.features |= PV_SUPPORTED_RTC;
         pv_init_ops = xen_init_ops;
         pv_apic_ops = xen_apic_ops;
         if (!xen_pvh_domain()) {