[PATCH v1 21/40] x86/cacheinfo: Consolidate AMD/Hygon leaf 0x8000001d calls

Ahmed S. Darwish
2025-03-04T08:53:18Z

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").

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
---
arch/x86/kernel/cpu/cacheinfo.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 0024d126c385..6aeabbd94997 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -598,23 +598,24 @@ cpuid4_cache_lookup_regs(int index, struct _cpuid4_info_regs *id4)
union _cpuid4_leaf_ecx ecx;
unsigned edx;

- if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
- if (boot_cpu_has(X86_FEATURE_TOPOEXT))
+ if (x86_vendor_amd_or_hygon(boot_cpu_data.x86_vendor)) {
+ if (boot_cpu_has(X86_FEATURE_TOPOEXT) ||
+ boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
+ /* AMD with TOPOEXT, or HYGON */
cpuid_count(0x8000001d, index, &eax.full,
&ebx.full, &ecx.full, &edx);
- else
+ } 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