linux-kernel - [PATCH v4 11/29] x86/cacheinfo: Consolidate AMD/Hygon leaf 0x8000001d calls

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Message-ID: <20250324133324.23458-12-darwi@linutronix.de>
Date: Mon, 24 Mar 2025 14:33:06 +0100
From: "Ahmed S. Darwish" <darwi@...utronix.de>
To: Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>
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 v4 11/29] x86/cacheinfo: Consolidate AMD/Hygon leaf 0x8000001d calls

While gathering CPU cache info, CPUID leaf 0x8000001d is invoked in two
separate if blocks: one for Hygon CPUs and one for AMDs with topology
extensions.  After each invocation, amd_init_l3_cache() is called.

Merge the two if blocks into a single condition, thus removing the
duplicated code.  Future commits will expand these if blocks, so
combining them now is both cleaner and more maintainable.

Note, while at it, remove a useless "better error?" comment that was
within the same function since the 2005 commit e2cac78935ff ("[PATCH]
x86_64: When running cpuid4 need to run on the correct CPU").

Note, as previously done at commit aec28d852ed2 ("x86/cpuid: Standardize
on u32 in <asm/cpuid/api.h>"), standardize on using 'u32' and 'u8' types.

Signed-off-by: Ahmed S. Darwish <darwi@...utronix.de>
---
 arch/x86/kernel/cpu/cacheinfo.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 1b2a2bf97d7f..f1055e806c9f 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -593,28 +593,28 @@ static void amd_init_l3_cache(struct _cpuid4_info_regs *id4, int index)
 static int
 cpuid4_cache_lookup_regs(int index, struct _cpuid4_info_regs *id4)
 {
-	union _cpuid4_leaf_eax	eax;
-	union _cpuid4_leaf_ebx	ebx;
-	union _cpuid4_leaf_ecx	ecx;
-	unsigned		edx;
-
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
-		if (boot_cpu_has(X86_FEATURE_TOPOEXT))
-			cpuid_count(0x8000001d, index, &eax.full,
-				    &ebx.full, &ecx.full, &edx);
-		else
+	u8 cpu_vendor = boot_cpu_data.x86_vendor;
+	union _cpuid4_leaf_eax eax;
+	union _cpuid4_leaf_ebx ebx;
+	union _cpuid4_leaf_ecx ecx;
+	u32 edx;
+
+	if (cpu_vendor == X86_VENDOR_AMD || cpu_vendor == X86_VENDOR_HYGON) {
+		if (boot_cpu_has(X86_FEATURE_TOPOEXT) || cpu_vendor == X86_VENDOR_HYGON) {
+			/* AMD with TOPOEXT, or HYGON */
+			cpuid_count(0x8000001d, index, &eax.full, &ebx.full, &ecx.full, &edx);
+		} else {
+			/* Legacy AMD fallback */
 			amd_cpuid4(index, &eax, &ebx, &ecx);
-		amd_init_l3_cache(id4, index);
-	} else if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
-		cpuid_count(0x8000001d, index, &eax.full,
-			    &ebx.full, &ecx.full, &edx);
+		}
 		amd_init_l3_cache(id4, index);
 	} else {
+		/* Intel */
 		cpuid_count(4, index, &eax.full, &ebx.full, &ecx.full, &edx);
 	}
 
 	if (eax.split.type == CTYPE_NULL)
-		return -EIO; /* better error ? */
+		return -EIO;
 
 	id4->eax = eax;
 	id4->ebx = ebx;
-- 
2.48.1