[PATCH 6.1.y] x86/init: Initialize wall clock in get_rtc_noop()

[Naman Jain <namjain@linux.microsoft.com>]

get_rtc_noop() is used when an RTC is unavailable, but leaves its output
argument untouched. When CONFIG_INIT_STACK_ALL_ZERO is not enabled,
timekeeping_init() may therefore receive a nonzero invalid persistent
clock value and warn:

  "Persistent clock returned invalid value"

Initialize the output to zero, the documented representation of an
unsupported persistent clock.

Fixes: c311ed6183f4 ("x86/init: Allow DT configured systems to disable RTC at boot time")
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Roman Kisel <vdso@mailbox.org>
Reviewed-by: Hardik Garg <hargar@linux.microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260831082528.1623843-1-namjain@linux.microsoft.com
(cherry picked from commit 7d5af1f256fdecff6a7986bbc9146b69cb355bb5)
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
---
 arch/x86/kernel/x86_init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index a4a921b9e6646..e911315c16a8c 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -35,7 +35,7 @@ static void iommu_shutdown_noop(void) { }
 bool __init bool_x86_init_noop(void) { return false; }
 void x86_op_int_noop(int cpu) { }
 static int set_rtc_noop(const struct timespec64 *now) { return -EINVAL; }
-static void get_rtc_noop(struct timespec64 *now) { }
+static void get_rtc_noop(struct timespec64 *now) { *now = (struct timespec64){0}; }
 
 static __initconst const struct of_device_id of_cmos_match[] = {
 	{ .compatible = "motorola,mc146818" },
-- 
2.43.0