ACPI: APEI: GHES: add TAINT_MACHINE_CHECK on GHES panic path

When a GHES (Generic Hardware Error Source) triggers a panic, add the
TAINT_MACHINE_CHECK taint flag to the kernel. This explicitly marks the
kernel as tainted due to a machine check event, improving diagnostics
and post-mortem analysis. The taint is set with LOCKDEP_STILL_OK to
indicate lockdep remains valid.

At large scale deployment, this helps to quickly determine panics that
are coming due to hardware failures.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://patch.msgid.link/20250702-add_tain-v1-1-9187b10914b9@debian.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: leitao

drivers/acpi/apei/ghes.c

@@ -1088,6 +1088,8 @@ static void __ghes_panic(struct ghes *ghes,
 
 	__ghes_print_estatus(KERN_EMERG, ghes->generic, estatus);
 
+	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_STILL_OK);
+
 	ghes_clear_estatus(ghes, estatus, buf_paddr, fixmap_idx);
 
 	if (!panic_timeout)