From 0bc03750deefc5fdab77b01c459bb1691c64c3c5 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Wed, 26 Nov 2025 12:51:47 +0000 Subject: [PATCH] x86/cpu: Drop vestigial PBE logic in AMD/Hygon/Centaur/Cyrix Besides formatting changes, this logic dates back to Linux 2.4.0-test11 in November 2000. Prior to "Massive cleanup of CPU detection and bug handling", c->x86_capability was a single u32 containing cpuid(1).edx, cpuid(0x80000001).edx, or a synthesis thereof. X86_FEATURE_AMD3D was defined as the top bit this single u32. After "Massive cleanup of CPU detection and bug handling", c->x86_capability became an array with AMD's extended feature leaf split away from Intel's basic feature leaf. AMD doc #20734-G states that 3DNow is only enumerated in the extended feature leaf, and that other vendors where using this bit too. i.e. AMD never produced a CPU which set bit 31 in the basic leaf, meaning that there's nothing to clear out in the first place. This logic looks like it was relevant in the pre-"Massive cleanup" world but ought to have been dropped when c->x86_capability was properly split. Signed-off-by: Andrew Cooper Signed-off-by: Ingo Molnar Cc: H. Peter Anvin Cc: Peter Zijlstra (Intel) Cc: Dave Hansen Cc: Pu Wen Link: https://patch.msgid.link/20251126125147.880275-1-andrew.cooper3@citrix.com --- arch/x86/kernel/cpu/amd.c | 6 ------ arch/x86/kernel/cpu/centaur.c | 6 ------ arch/x86/kernel/cpu/cyrix.c | 6 ------ arch/x86/kernel/cpu/hygon.c | 6 ------ 4 files changed, 24 deletions(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index c04f53f43af1d..c792c2afd8499 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -1051,12 +1051,6 @@ static void init_amd(struct cpuinfo_x86 *c) early_init_amd(c); - /* - * Bit 31 in normal CPUID used for nonstandard 3DNow ID; - * 3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway - */ - clear_cpu_cap(c, 0*32+31); - if (c->x86 >= 0x10) set_cpu_cap(c, X86_FEATURE_REP_GOOD); diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c index a3b55db35c961..c8398940b9752 100644 --- a/arch/x86/kernel/cpu/centaur.c +++ b/arch/x86/kernel/cpu/centaur.c @@ -119,12 +119,6 @@ static void init_centaur(struct cpuinfo_x86 *c) u32 fcr_clr = 0; u32 lo, hi, newlo; u32 aa, bb, cc, dd; - - /* - * Bit 31 in normal CPUID used for nonstandard 3DNow ID; - * 3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway - */ - clear_cpu_cap(c, 0*32+31); #endif early_init_centaur(c); init_intel_cacheinfo(c); diff --git a/arch/x86/kernel/cpu/cyrix.c b/arch/x86/kernel/cpu/cyrix.c index dfec2c61e3547..8f22085c4dd23 100644 --- a/arch/x86/kernel/cpu/cyrix.c +++ b/arch/x86/kernel/cpu/cyrix.c @@ -195,12 +195,6 @@ static void init_cyrix(struct cpuinfo_x86 *c) char *buf = c->x86_model_id; const char *p = NULL; - /* - * Bit 31 in normal CPUID used for nonstandard 3DNow ID; - * 3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway - */ - clear_cpu_cap(c, 0*32+31); - /* Cyrix used bit 24 in extended (AMD) CPUID for Cyrix MMX extensions */ if (test_cpu_cap(c, 1*32+24)) { clear_cpu_cap(c, 1*32+24); diff --git a/arch/x86/kernel/cpu/hygon.c b/arch/x86/kernel/cpu/hygon.c index 1fda6c3a2b65a..7f95a74e4c657 100644 --- a/arch/x86/kernel/cpu/hygon.c +++ b/arch/x86/kernel/cpu/hygon.c @@ -174,12 +174,6 @@ static void init_hygon(struct cpuinfo_x86 *c) early_init_hygon(c); - /* - * Bit 31 in normal CPUID used for nonstandard 3DNow ID; - * 3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway - */ - clear_cpu_cap(c, 0*32+31); - set_cpu_cap(c, X86_FEATURE_REP_GOOD); /* -- 2.47.3