[Naman Jain (namancse)]

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: c311ed6 ("x86/init: Allow DT configured systems to disable RTC at boot time")
Cc: stable@vger.kernel.org
Reviewed-by: Thomas Gleixner tglx@kernel.org
Reviewed-by: Roman Kisel vdso@mailbox.org
Reviewed-by: Dexuan Cui decui@microsoft.com
Reviewed-by: Hardik Garg hargar@linux.microsoft.com
Link: https://lore.kernel.org/all/20260831082528.1623843-1-namjain@linux.microsoft.com/
Reviewed, but not picked in mainline at the time of backporting.

[Copilot]

🟢 Approval recommended

The localized change correctly initializes the output to zero and has no unresolved review findings.

No open issues 🎉

What changed in this PR

This PR fixes the x86 fallback used when no RTC is available by returning a zero persistent-clock value instead of leaving the output uninitialized.

Changes:

• Zero-initialize the timespec64 output in get_rtc_noop().
• Prevent invalid persistent-clock warnings caused by uninitialized stack data.

File	Description
arch/​x86/​kernel/​x86_init.c	Initialize the no-RTC clock output to the documented unsupported-clock value.

_{Review effort: Balanced}