linux-kernel - [PATCH v2 13/20] tools/x86/kcpuid: Consolidate index validity checks

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Message-ID: <20250312143738.458507-14-darwi@linutronix.de>
Date: Wed, 12 Mar 2025 15:37:30 +0100
From: "Ahmed S. Darwish" <darwi@...utronix.de>
To: Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	John Ogness <john.ogness@...utronix.de>,
	x86@...nel.org,
	x86-cpuid@...ts.linux.dev,
	LKML <linux-kernel@...r.kernel.org>,
	"Ahmed S. Darwish" <darwi@...utronix.de>
Subject: [PATCH v2 13/20] tools/x86/kcpuid: Consolidate index validity checks

Let index_to_cpuid_range() return a range only if the passed index is
within that range's maximum supported function on the CPU.

This avoids repeating the same index validity check at both
setup_cpuid_range() and index_to_func().

Signed-off-by: Ahmed S. Darwish <darwi@...utronix.de>
---
 tools/arch/x86/kcpuid/kcpuid.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/tools/arch/x86/kcpuid/kcpuid.c b/tools/arch/x86/kcpuid/kcpuid.c
index 0ba0d440482c..fff6db1119ed 100644
--- a/tools/arch/x86/kcpuid/kcpuid.c
+++ b/tools/arch/x86/kcpuid/kcpuid.c
@@ -101,10 +101,12 @@ static char *range_to_str(struct cpuid_range *range)
 
 struct cpuid_range *index_to_cpuid_range(u32 index)
 {
+	u32 func_idx = index & CPUID_FUNCTION_MASK;
+	u32 range_idx = index & CPUID_INDEX_MASK;
 	struct cpuid_range *range;
 
 	for_each_cpuid_range(range) {
-		if (range->index == (index & CPUID_INDEX_MASK))
+		if (range->index == range_idx && (u32)range->nr > func_idx)
 			return range;
 	}
 
@@ -331,16 +333,14 @@ static void parse_line(char *line)
 	/* index/main-leaf */
 	index = strtoull(tokens[0], NULL, 0);
 
-	/* Skip line parsing if it's not covered by known ranges */
+	/*
+	 * Skip line parsing if the index is not covered by known-valid
+	 * CPUID ranges on this CPU.
+	 */
 	range = index_to_cpuid_range(index);
 	if (!range)
 		return;
 
-	/* Skip line parsing for non-existing indexes */
-	index &= CPUID_FUNCTION_MASK;
-	if ((int)index >= range->nr)
-		return;
-
 	/* Skip line parsing if the index CPUID output is all zero */
 	func = &range->funcs[index];
 	if (!func->nr)
@@ -505,17 +505,13 @@ static void show_range(struct cpuid_range *range)
 
 static inline struct cpuid_func *index_to_func(u32 index)
 {
+	u32 func_idx = index & CPUID_FUNCTION_MASK;
 	struct cpuid_range *range;
-	u32 func_idx;
 
 	range = index_to_cpuid_range(index);
 	if (!range)
 		return NULL;
 
-	func_idx = index & CPUID_FUNCTION_MASK;
-	if ((func_idx + 1) > (u32)range->nr)
-		return NULL;
-
 	return &range->funcs[func_idx];
 }
 
-- 
2.48.1