0604-x86-time-Don-t-use-EFI-s-GetTime-call-by-default.patch

From d84e22ff2a88663e5dcb3cdced45faf2aac2fac1 Mon Sep 17 00:00:00 2001
From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Date: Tue, 1 Dec 2015 16:57:46 +0000
Subject: [PATCH] x86/time: Don't use EFI's GetTime call by default

When EFI is used, don't use EFI's GetTime() to get the time, because it
is broken on many platforms. From Linux commit 7efe665903d0 ("rtc:
Disable EFI rtc for x86"):
"Disable it explicitly for x86 so that we don't give users false
hope that this driver will work - it won't, and your machine is likely
to crash."

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
 xen/arch/x86/time.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index a97d78484105..45f6baf6270b 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1245,20 +1245,25 @@ static void __get_cmos_time(struct rtc_time *rtc)
         rtc->year += 100;
 }
 
+/* EFI's GetTime() is frequently broken so don't use it by default. */
+#undef USE_EFI_GET_TIME
+
 static unsigned long get_cmos_time(void)
 {
-    unsigned long res, flags;
+    unsigned long flags;
     struct rtc_time rtc;
     unsigned int seconds = 60;
     static bool __read_mostly cmos_rtc_probe;
     boolean_param("cmos-rtc-probe", cmos_rtc_probe);
 
+#ifdef USE_EFI_GET_TIME
     if ( efi_enabled(EFI_RS) )
     {
-        res = efi_get_time();
+        unsigned long res = efi_get_time();
         if ( res )
             return res;
     }
+#endif
 
     if ( likely(!(acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC)) )
         cmos_rtc_probe = false;
-- 
2.44.0