x86/fpu/xstate: Fix XSTATE_WARN_ON() to emit relevant diagnostics

"XSAVE consistency problem" has been reported under Xen, but that's the extent
of my divination skills.

Modify XSTATE_WARN_ON() to force the caller to provide relevant diagnostic
information, and modify each caller suitably.

For check_xstate_against_struct(), this removes a double WARN() where one will
do perfectly fine.

CC stable as this has been wonky debugging for 7 years and it is good to
have there too.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220810221909.12768-1-andrew.cooper3@citrix.com

arch/x86/kernel/fpu/xstate.c

@@ -440,8 +440,8 @@ static void __init __xstate_dump_leaves(void)
 	}
 }
 
-#define XSTATE_WARN_ON(x) do {							\
-	if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {	\
+#define XSTATE_WARN_ON(x, fmt, ...) do {					\
+	if (WARN_ONCE(x, "XSAVE consistency problem: " fmt, ##__VA_ARGS__)) {	\
 		__xstate_dump_leaves();						\
 	}									\
 } while (0)
@@ -554,8 +554,7 @@ static bool __init check_xstate_against_struct(int nr)
 	    (nr >= XFEATURE_MAX) ||
 	    (nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR) ||
 	    ((nr >= XFEATURE_RSRVD_COMP_11) && (nr <= XFEATURE_RSRVD_COMP_16))) {
-		WARN_ONCE(1, "no structure for xstate: %d\n", nr);
-		XSTATE_WARN_ON(1);
+		XSTATE_WARN_ON(1, "No structure for xstate: %d\n", nr);
 		return false;
 	}
 	return true;
@@ -598,12 +597,13 @@ static bool __init paranoid_xstate_size_valid(unsigned int kernel_size)
 		 * XSAVES.
 		 */
 		if (!xsaves && xfeature_is_supervisor(i)) {
-			XSTATE_WARN_ON(1);
+			XSTATE_WARN_ON(1, "Got supervisor feature %d, but XSAVES not advertised\n", i);
 			return false;
 		}
 	}
 	size = xstate_calculate_size(fpu_kernel_cfg.max_features, compacted);
-	XSTATE_WARN_ON(size != kernel_size);
+	XSTATE_WARN_ON(size != kernel_size,
+		       "size %u != kernel_size %u\n", size, kernel_size);
 	return size == kernel_size;
 }