[PATCH v7 040/120] x86/cpu/amd: Use parsed CPUID(0x80000005)

"Ahmed S. Darwish" <[email protected]> Thu, 28 May 2026 17:38:02 +0200
Newsgroups dev.linux.lists.x86-cpuid,org.kernel.vger.linux-kernel
Message-ID <[email protected]>
For AMD BSP init, use parsed CPUID(0x80000005) instead of issuing a direct
CPUID query and doing ugly bitwise operations.

Signed-off-by: Ahmed S. Darwish <[email protected]>
---
 arch/x86/kernel/cpu/amd.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 62f74a7f2f8d..4fa16f2fd402 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -4,6 +4,7 @@
 #include <linux/dmi.h>
 #include <linux/elf.h>
 #include <linux/mm.h>
+#include <linux/sizes.h>
 #include <linux/kvm_types.h>
 #include <linux/io.h>
 #include <linux/sched.h>
@@ -422,6 +423,8 @@ static void tsa_init(struct cpuinfo_x86 *c)
 
 static void bsp_init_amd(struct cpuinfo_x86 *c)
 {
+	const struct leaf_0x80000005_0 *el5 = cpuid_leaf(c, 0x80000005);
+
 	if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) {
 
 		if (c->x86 > 0x10 ||
@@ -434,13 +437,8 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 		}
 	}
 
-	if (c->x86 == 0x15) {
-		unsigned long upperbit;
-		u32 cpuid, assoc;
-
-		cpuid	 = cpuid_edx(0x80000005);
-		assoc	 = cpuid >> 16 & 0xff;
-		upperbit = ((cpuid >> 24) << 10) / assoc;
+	if (c->x86 == 0x15 && el5) {
+		unsigned long upperbit = (el5->l1_icache_size_kb * SZ_1K) / el5->l1_icache_assoc;
 
 		va_align.mask	  = (upperbit - 1) & PAGE_MASK;
 		va_align.flags    = ALIGN_VA_32 | ALIGN_VA_64;
-- 
2.54.0