[Xen-devel] [PATCH] x86/time: Don't use EFI's GetTime call by default

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

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 | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 30d52c4..28895c2 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -679,20 +679,28 @@ 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;
+#ifdef USE_EFI_GET_TIME
+    unsigned long res;
+#endif
+    unsigned long flags;
     struct rtc_time rtc;
     unsigned int seconds = 60;
     static bool_t __read_mostly cmos_rtc_probe;
     boolean_param("cmos-rtc-probe", cmos_rtc_probe);
 
+#ifdef USE_EFI_GET_TIME
     if ( efi_enabled )
     {
         res = efi_get_time();
         if ( res )
             return res;
     }
+#endif
 
     if ( likely(!(acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC)) )
         cmos_rtc_probe = 0;
-- 
2.4.3


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