From a87d131a8c2952e53ba9ed513d5553426cdeac34 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Tue, 16 May 2023 14:07:43 +0100 Subject: [PATCH] x86/cpufeature: Rework {boot_,}cpu_has() One area where Xen deviates from Linux is that test_bit() forces a volatile read. This leads to poor code generation, because the optimiser cannot merge bit operations on the same word. Drop the use of test_bit(), and write the expressions in regular C. This removes the include of bitops.h (which is a frequent source of header tangles), and it offers the optimiser far more flexibility. Bloat-o-meter reports a net change of: add/remove: 0/0 grow/shrink: 21/87 up/down: 641/-2751 (-2110) with half of that in x86_emulate() alone. vmx_ctxt_switch_to() seems to be the fastpath with the greatest delta at -24, where the optimiser has successfully removed the branch hidden in cpu_has_msr_tsc_aux. No functional change. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- xen/arch/x86/include/asm/cpufeature.h | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/xen/arch/x86/include/asm/cpufeature.h b/xen/arch/x86/include/asm/cpufeature.h index 4140ec0938..d0ead8e7a5 100644 --- a/xen/arch/x86/include/asm/cpufeature.h +++ b/xen/arch/x86/include/asm/cpufeature.h @@ -17,7 +17,6 @@ #define X86_FEATURE_ALWAYS X86_FEATURE_LM #ifndef __ASSEMBLY__ -#include struct cpuinfo_x86 { unsigned char x86; /* CPU family */ @@ -43,8 +42,15 @@ struct cpuinfo_x86 { extern struct cpuinfo_x86 boot_cpu_data; -#define cpu_has(c, bit) test_bit(bit, (c)->x86_capability) -#define boot_cpu_has(bit) test_bit(bit, boot_cpu_data.x86_capability) +static inline bool cpu_has(const struct cpuinfo_x86 *info, unsigned int feat) +{ + return info->x86_capability[cpufeat_word(feat)] & cpufeat_mask(feat); +} + +static inline bool boot_cpu_has(unsigned int feat) +{ + return cpu_has(&boot_cpu_data, feat); +} #define CPUID_PM_LEAF 6 #define CPUID6_ECX_APERFMPERF_CAPABILITY 0x1 -- 2.39.5