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107e6a3c22
Support usable check for all CPU features with the following changes:
1. Change struct cpu_features to
struct cpuid_features
{
struct cpuid_registers cpuid;
struct cpuid_registers usable;
};
struct cpu_features
{
struct cpu_features_basic basic;
struct cpuid_features features[COMMON_CPUID_INDEX_MAX];
unsigned int preferred[PREFERRED_FEATURE_INDEX_MAX];
...
};
so that there is a usable bit for each cpuid bit.
2. After the cpuid bits have been initialized, copy the known bits to the
usable bits. EAX/EBX from INDEX_1 and EAX from INDEX_7 aren't used for
CPU feature detection.
3. Clear the usable bits which require OS support.
4. If the feature is supported by OS, copy its cpuid bit to its usable
bit.
5. Replace HAS_CPU_FEATURE and CPU_FEATURES_CPU_P with CPU_FEATURE_USABLE
and CPU_FEATURE_USABLE_P to check if a feature is usable.
6. Add DEPR_FPU_CS_DS for INDEX_7_EBX_13.
7. Unset MPX feature since it has been deprecated.
The results are
1. If the feature is known and doesn't requre OS support, its usable bit
is copied from the cpuid bit.
2. Otherwise, its usable bit is copied from the cpuid bit only if the
feature is known to supported by OS.
3. CPU_FEATURE_USABLE/CPU_FEATURE_USABLE_P are used to check if the
feature can be used.
4. HAS_CPU_FEATURE/CPU_FEATURE_CPU_P are used to check if CPU supports
the feature.
323 lines
9.6 KiB
C
323 lines
9.6 KiB
C
/* x86 CPU feature tuning.
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This file is part of the GNU C Library.
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Copyright (C) 2017-2020 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#if HAVE_TUNABLES
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# define TUNABLE_NAMESPACE cpu
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# include <stdbool.h>
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# include <stdint.h>
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# include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
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# include <elf/dl-tunables.h>
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# include <string.h>
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# include <cpu-features.h>
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# include <ldsodefs.h>
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/* We can't use IFUNC memcmp nor strlen in init_cpu_features from libc.a
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since IFUNC must be set up by init_cpu_features. */
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# if defined USE_MULTIARCH && !defined SHARED
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# ifdef __x86_64__
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# define DEFAULT_MEMCMP __memcmp_sse2
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# else
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# define DEFAULT_MEMCMP __memcmp_ia32
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# endif
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extern __typeof (memcmp) DEFAULT_MEMCMP;
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# else
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# define DEFAULT_MEMCMP memcmp
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# endif
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# define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (!DEFAULT_MEMCMP (f, #name, len)) \
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{ \
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CPU_FEATURE_UNSET (cpu_features, name) \
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break; \
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}
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/* Disable a preferred feature NAME. We don't enable a preferred feature
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which isn't available. */
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# define CHECK_GLIBC_IFUNC_PREFERRED_OFF(f, cpu_features, name, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (!DEFAULT_MEMCMP (f, #name, len)) \
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{ \
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cpu_features->preferred[index_arch_##name] \
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&= ~bit_arch_##name; \
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break; \
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}
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/* Enable/disable a preferred feature NAME. */
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# define CHECK_GLIBC_IFUNC_PREFERRED_BOTH(f, cpu_features, name, \
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disable, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (!DEFAULT_MEMCMP (f, #name, len)) \
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{ \
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if (disable) \
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cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
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else \
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cpu_features->preferred[index_arch_##name] |= bit_arch_##name; \
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break; \
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}
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/* Enable/disable a preferred feature NAME. Enable a preferred feature
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only if the feature NEED is usable. */
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# define CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH(f, cpu_features, name, \
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need, disable, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (!DEFAULT_MEMCMP (f, #name, len)) \
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{ \
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if (disable) \
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cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
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else if (CPU_FEATURE_USABLE_P (cpu_features, need)) \
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cpu_features->preferred[index_arch_##name] |= bit_arch_##name; \
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break; \
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}
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attribute_hidden
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void
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TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
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{
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/* The current IFUNC selection is based on microbenchmarks in glibc.
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It should give the best performance for most workloads. But other
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choices may have better performance for a particular workload or on
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the hardware which wasn't available when the selection was made.
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The environment variable:
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GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,-zzz,....
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can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature
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yyy and zzz, where the feature name is case-sensitive and has to
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match the ones in cpu-features.h. It can be used by glibc developers
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to tune for a new processor or override the IFUNC selection to
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improve performance for a particular workload.
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NOTE: the IFUNC selection may change over time. Please check all
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multiarch implementations when experimenting. */
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const char *p = valp->strval;
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struct cpu_features *cpu_features = &GLRO(dl_x86_cpu_features);
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size_t len;
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do
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{
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const char *c, *n;
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bool disable;
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size_t nl;
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for (c = p; *c != ','; c++)
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if (*c == '\0')
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break;
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len = c - p;
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disable = *p == '-';
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if (disable)
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{
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n = p + 1;
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nl = len - 1;
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}
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else
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{
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n = p;
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nl = len;
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}
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switch (nl)
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{
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default:
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break;
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case 3:
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if (disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CX8, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, HTT, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, IBT, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, RTM, 3);
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}
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break;
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case 4:
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if (disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX2, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI1, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI2, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CMOV, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, ERMS, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA4, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE2, 4);
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CHECK_GLIBC_IFUNC_PREFERRED_OFF (n, cpu_features, I586, 4);
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CHECK_GLIBC_IFUNC_PREFERRED_OFF (n, cpu_features, I686, 4);
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}
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break;
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case 5:
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if (disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, LZCNT, 5);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, MOVBE, 5);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SHSTK, 5);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSSE3, 5);
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}
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break;
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case 6:
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if (disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6);
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if (!DEFAULT_MEMCMP (n, "XSAVEC", 6))
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{
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/* Update xsave_state_size to XSAVE state size. */
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cpu_features->xsave_state_size
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= cpu_features->xsave_state_full_size;
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CPU_FEATURE_UNSET (cpu_features, XSAVEC);
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}
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}
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break;
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case 7:
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if (disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512F, 7);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, OSXSAVE, 7);
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}
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break;
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case 8:
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if (disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512CD, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512BW, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512DQ, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512ER, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512PF, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512VL, 8);
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}
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Slow_BSF,
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disable, 8);
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break;
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case 11:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Prefer_ERMS,
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disable, 11);
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Prefer_FSRM,
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disable, 11);
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH (n, cpu_features,
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Slow_SSE4_2,
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SSE4_2,
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disable, 11);
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}
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break;
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case 15:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Rep_String,
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disable, 15);
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}
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break;
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case 16:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, Prefer_No_AVX512, AVX512F,
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disable, 16);
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}
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break;
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case 18:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Copy_Backward,
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disable, 18);
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}
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break;
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case 19:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Unaligned_Load,
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disable, 19);
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Unaligned_Copy,
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disable, 19);
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}
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break;
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case 20:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, Prefer_No_VZEROUPPER, AVX, disable,
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20);
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}
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break;
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case 21:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Prefer_MAP_32BIT_EXEC,
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disable, 21);
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}
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break;
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case 23:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, AVX_Fast_Unaligned_Load, AVX,
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disable, 23);
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}
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break;
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case 24:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, MathVec_Prefer_No_AVX512, AVX512F,
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disable, 24);
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}
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break;
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case 26:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, Prefer_PMINUB_for_stringop, SSE2,
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disable, 26);
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}
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break;
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}
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p += len + 1;
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}
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while (*p != '\0');
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}
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# if CET_ENABLED
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attribute_hidden
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void
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TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
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{
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if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
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GL(dl_x86_feature_control).ibt = cet_always_on;
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else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
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GL(dl_x86_feature_control).ibt = cet_always_off;
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else if (DEFAULT_MEMCMP (valp->strval, "permissive",
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sizeof ("permissive")) == 0)
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GL(dl_x86_feature_control).ibt = cet_permissive;
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}
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attribute_hidden
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void
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TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *valp)
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{
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if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
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GL(dl_x86_feature_control).shstk = cet_always_on;
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else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
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GL(dl_x86_feature_control).shstk = cet_always_off;
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else if (DEFAULT_MEMCMP (valp->strval, "permissive",
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sizeof ("permissive")) == 0)
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GL(dl_x86_feature_control).shstk = cet_permissive;
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}
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# endif
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#endif
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