Re: [PATCH v2 2/8] x86/cpu: Get LLC ID for Hygon family 18h model 4h

[Borislav Petkov]

On Tue, Apr 07, 2026 at 04:23:09PM +0800, Fu Hao wrote:
> Add support to calculate LLC ID from the number of threads sharing
> the cache for Hygon family 18h model 4h processor.
> 
> Signed-off-by: Fu Hao <fuhao@xxxxxxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/cacheinfo.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)

If you're going to copy code at least try to share functionality which is
kinda begging to be a separate function.

Ontop of yours and untested:

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 98862afc4e55..8e51226aee74 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -305,10 +305,19 @@ static unsigned int get_cache_id(u32 apicid, const struct _cpuid4_info *id4)
 	return apicid >> index_msb;
 }
 
+/* LLC ID is calculated from the number of threads sharing the L3 cache. */
+static void __calc_llc_id(struct cpuinfo_x86 *c)
+{
+	u32 llc_index = find_num_cache_leaves(c) - 1;
+	struct _cpuid4_info id4 = {};
+
+	if (!amd_fill_cpuid4_info(llc_index, &id4))
+		c->topo.llc_id = get_cache_id(c->topo.apicid, &id4);
+}
+
 /*
  * AMD/Hygon CPUs may have multiple LLCs if L3 caches exist.
  */
-
 void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, u16 die_id)
 {
 	if (!cpuid_amd_hygon_has_l3_cache())
@@ -324,15 +333,7 @@ void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, u16 die_id)
 		 */
 		c->topo.llc_id = c->topo.apicid >> 3;
 	} else {
-		/*
-		 * Newer families: LLC ID is calculated from the number
-		 * of threads sharing the L3 cache.
-		 */
-		u32 llc_index = find_num_cache_leaves(c) - 1;
-		struct _cpuid4_info id4 = {};
-
-		if (!amd_fill_cpuid4_info(llc_index, &id4))
-			c->topo.llc_id = get_cache_id(c->topo.apicid, &id4);
+		__calc_llc_id(c);
 	}
 }
 
@@ -342,15 +343,7 @@ void cacheinfo_hygon_init_llc_id(struct cpuinfo_x86 *c)
 		return;
 
 	if (c->x86_model >= 0x4) {
-		/*
-		 * From model 4h: LLC ID is calculated from the number
-		 * of threads sharing the L3 cache.
-		 */
-		u32 llc_index = find_num_cache_leaves(c) - 1;
-		struct _cpuid4_info id4 = {};
-
-		if (!amd_fill_cpuid4_info(llc_index, &id4))
-			c->topo.llc_id = get_cache_id(c->topo.apicid, &id4);
+		__calc_llc_id(c);
 	} else {
 		/*
 		 * The others are similar to AMD Family 17h up to 1F models: LLC is

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette