From: K Prateek Nayak Date: Thu, 21 Aug 2025 05:19:09 +0000 (+0000) Subject: x86/cpu/cacheinfo: Simplify cacheinfo_amd_init_llc_id() using _cpuid4_info X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=af507c6951180ae5e5edb71f56a227ffdcc54f78;p=users%2Fhch%2Fmisc.git x86/cpu/cacheinfo: Simplify cacheinfo_amd_init_llc_id() using _cpuid4_info struct _cpuid4_info has the same layout as the CPUID leaf 0x8000001d. Use the encoded definition and amd_fill_cpuid4_info(), get_cache_id() helpers instead of open coding masks and shifts to calculate the llc_id. cacheinfo_amd_init_llc_id() is only called on AMD systems that support X86_FEATURE_TOPOEXT and amd_fill_cpuid4_info() uses the information from CPUID leaf 0x8000001d on all these systems which is consistent with the current open coded implementation. While at it, avoid reading cpu_data() every time get_cache_id() is called and instead pass the APIC ID necessary to return the _cpuid4_info.id from get_cache_id(). No functional changes intended. [ bp: do what Ahmed suggests: merge into one patch, make id4 ptr const. ] Signed-off-by: K Prateek Nayak Signed-off-by: Borislav Petkov (AMD) Signed-off-by: Ingo Molnar Acked-by: Ahmed S. Darwish Link: https://lore.kernel.org/20250821051910.7351-2-kprateek.nayak@amd.com --- diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c index adfa7e8bb865..51a95b07831f 100644 --- a/arch/x86/kernel/cpu/cacheinfo.c +++ b/arch/x86/kernel/cpu/cacheinfo.c @@ -289,6 +289,22 @@ static int find_num_cache_leaves(struct cpuinfo_x86 *c) return i; } +/* + * The max shared threads number comes from CPUID(0x4) EAX[25-14] with input + * ECX as cache index. Then right shift apicid by the number's order to get + * cache id for this cache node. + */ +static unsigned int get_cache_id(u32 apicid, const struct _cpuid4_info *id4) +{ + unsigned long num_threads_sharing; + int index_msb; + + num_threads_sharing = 1 + id4->eax.split.num_threads_sharing; + index_msb = get_count_order(num_threads_sharing); + + return apicid >> index_msb; +} + /* * AMD/Hygon CPUs may have multiple LLCs if L3 caches exist. */ @@ -312,18 +328,11 @@ void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, u16 die_id) * Newer families: LLC ID is calculated from the number * of threads sharing the L3 cache. */ - u32 eax, ebx, ecx, edx, num_sharing_cache = 0; u32 llc_index = find_num_cache_leaves(c) - 1; + struct _cpuid4_info id4 = {}; - cpuid_count(0x8000001d, llc_index, &eax, &ebx, &ecx, &edx); - if (eax) - num_sharing_cache = ((eax >> 14) & 0xfff) + 1; - - if (num_sharing_cache) { - int index_msb = get_count_order(num_sharing_cache); - - c->topo.llc_id = c->topo.apicid >> index_msb; - } + if (!amd_fill_cpuid4_info(llc_index, &id4)) + c->topo.llc_id = get_cache_id(c->topo.apicid, &id4); } } @@ -598,27 +607,12 @@ int init_cache_level(unsigned int cpu) return 0; } -/* - * The max shared threads number comes from CPUID(0x4) EAX[25-14] with input - * ECX as cache index. Then right shift apicid by the number's order to get - * cache id for this cache node. - */ -static void get_cache_id(int cpu, struct _cpuid4_info *id4) -{ - struct cpuinfo_x86 *c = &cpu_data(cpu); - unsigned long num_threads_sharing; - int index_msb; - - num_threads_sharing = 1 + id4->eax.split.num_threads_sharing; - index_msb = get_count_order(num_threads_sharing); - id4->id = c->topo.apicid >> index_msb; -} - int populate_cache_leaves(unsigned int cpu) { struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu); struct cacheinfo *ci = this_cpu_ci->info_list; u8 cpu_vendor = boot_cpu_data.x86_vendor; + u32 apicid = cpu_data(cpu).topo.apicid; struct amd_northbridge *nb = NULL; struct _cpuid4_info id4 = {}; int idx, ret; @@ -628,7 +622,7 @@ int populate_cache_leaves(unsigned int cpu) if (ret) return ret; - get_cache_id(cpu, &id4); + id4.id = get_cache_id(apicid, &id4); if (cpu_vendor == X86_VENDOR_AMD || cpu_vendor == X86_VENDOR_HYGON) nb = amd_init_l3_cache(idx);