x86: make PV hypercall entry points work with !CONFIG_PV

We want Xen to crash if we hit these paths when PV is disabled.

For syscall, we provide stubs for {l,c}star_enter which end up calling
panic.  For sysenter, we initialise CS to 0 so that #GP can be raised.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/arch/x86/hvm/vmx/vmcs.c

@@ -1160,8 +1160,9 @@ static int construct_vmcs(struct vcpu *v)
     __vmwrite(HOST_RIP, (unsigned long)vmx_asm_vmexit_handler);
 
     /* Host SYSENTER CS:RIP. */
-    __vmwrite(HOST_SYSENTER_CS, __HYPERVISOR_CS);
-    __vmwrite(HOST_SYSENTER_EIP, (unsigned long)sysenter_entry);
+    __vmwrite(HOST_SYSENTER_CS, IS_ENABLED(CONFIG_PV) ? __HYPERVISOR_CS : 0);
+    __vmwrite(HOST_SYSENTER_EIP,
+              IS_ENABLED(CONFIG_PV) ? (unsigned long)sysenter_entry : 0);
 
     /* MSR intercepts. */
     __vmwrite(VM_EXIT_MSR_LOAD_COUNT, 0);

xen/arch/x86/x86_64/traps.c

@@ -298,8 +298,21 @@ static unsigned int write_stub_trampoline(
 }
 
 DEFINE_PER_CPU(struct stubs, stubs);
+
+#ifdef CONFIG_PV
 void lstar_enter(void);
 void cstar_enter(void);
+#else
+static inline void lstar_enter(void)
+{
+    panic("%s called\n", __func__);
+}
+
+static inline void cstar_enter(void)
+{
+    panic("%s called\n", __func__);
+}
+#endif /* CONFIG_PV */
 
 void subarch_percpu_traps_init(void)
 {
@@ -329,8 +342,10 @@ void subarch_percpu_traps_init(void)
     {
         /* SYSENTER entry. */
         wrmsrl(MSR_IA32_SYSENTER_ESP, stack_bottom);
-        wrmsrl(MSR_IA32_SYSENTER_EIP, (unsigned long)sysenter_entry);
-        wrmsr(MSR_IA32_SYSENTER_CS, __HYPERVISOR_CS, 0);
+        wrmsrl(MSR_IA32_SYSENTER_EIP,
+               IS_ENABLED(CONFIG_PV) ? (unsigned long)sysenter_entry : 0);
+        wrmsr(MSR_IA32_SYSENTER_CS,
+              IS_ENABLED(CONFIG_PV) ? __HYPERVISOR_CS : 0, 0);
     }
 
     /* Trampoline for SYSCALL entry from compatibility mode. */