diff options
Diffstat (limited to 'arch/x86/kernel/fpu/init.c')
| -rw-r--r-- | arch/x86/kernel/fpu/init.c | 161 |
1 files changed, 83 insertions, 78 deletions
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index 7b2978ab30df..6d9f0a7ef4c8 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -3,8 +3,11 @@ */ #include <asm/fpu/internal.h> #include <asm/tlbflush.h> +#include <asm/setup.h> +#include <asm/cmdline.h> #include <linux/sched.h> +#include <linux/init.h> /* * Initialize the TS bit in CR0 according to the style of context-switches @@ -270,20 +273,52 @@ static void __init fpu__init_system_xstate_size_legacy(void) */ static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO; -static int __init eager_fpu_setup(char *s) +/* + * Find supported xfeatures based on cpu features and command-line input. + * This must be called after fpu__init_parse_early_param() is called and + * xfeatures_mask is enumerated. + */ +u64 __init fpu__get_supported_xfeatures_mask(void) { - if (!strcmp(s, "on")) - eagerfpu = ENABLE; - else if (!strcmp(s, "off")) - eagerfpu = DISABLE; - else if (!strcmp(s, "auto")) - eagerfpu = AUTO; - return 1; + /* Support all xfeatures known to us */ + if (eagerfpu != DISABLE) + return XCNTXT_MASK; + + /* Warning of xfeatures being disabled for no eagerfpu mode */ + if (xfeatures_mask & XFEATURE_MASK_EAGER) { + pr_err("x86/fpu: eagerfpu switching disabled, disabling the following xstate features: 0x%llx.\n", + xfeatures_mask & XFEATURE_MASK_EAGER); + } + + /* Return a mask that masks out all features requiring eagerfpu mode */ + return ~XFEATURE_MASK_EAGER; +} + +/* + * Disable features dependent on eagerfpu. + */ +static void __init fpu__clear_eager_fpu_features(void) +{ + setup_clear_cpu_cap(X86_FEATURE_MPX); + setup_clear_cpu_cap(X86_FEATURE_AVX); + setup_clear_cpu_cap(X86_FEATURE_AVX2); + setup_clear_cpu_cap(X86_FEATURE_AVX512F); + setup_clear_cpu_cap(X86_FEATURE_AVX512PF); + setup_clear_cpu_cap(X86_FEATURE_AVX512ER); + setup_clear_cpu_cap(X86_FEATURE_AVX512CD); } -__setup("eagerfpu=", eager_fpu_setup); /* * Pick the FPU context switching strategy: + * + * When eagerfpu is AUTO or ENABLE, we ensure it is ENABLE if either of + * the following is true: + * + * (1) the cpu has xsaveopt, as it has the optimization and doing eager + * FPU switching has a relatively low cost compared to a plain xsave; + * (2) the cpu has xsave features (e.g. MPX) that depend on eager FPU + * switching. Should the kernel boot with noxsaveopt, we support MPX + * with eager FPU switching at a higher cost. */ static void __init fpu__init_system_ctx_switch(void) { @@ -295,19 +330,11 @@ static void __init fpu__init_system_ctx_switch(void) WARN_ON_FPU(current->thread.fpu.fpstate_active); current_thread_info()->status = 0; - /* Auto enable eagerfpu for xsaveopt */ if (boot_cpu_has(X86_FEATURE_XSAVEOPT) && eagerfpu != DISABLE) eagerfpu = ENABLE; - if (xfeatures_mask & XFEATURE_MASK_EAGER) { - if (eagerfpu == DISABLE) { - pr_err("x86/fpu: eagerfpu switching disabled, disabling the following xstate features: 0x%llx.\n", - xfeatures_mask & XFEATURE_MASK_EAGER); - xfeatures_mask &= ~XFEATURE_MASK_EAGER; - } else { - eagerfpu = ENABLE; - } - } + if (xfeatures_mask & XFEATURE_MASK_EAGER) + eagerfpu = ENABLE; if (eagerfpu == ENABLE) setup_force_cpu_cap(X86_FEATURE_EAGER_FPU); @@ -316,11 +343,48 @@ static void __init fpu__init_system_ctx_switch(void) } /* + * We parse fpu parameters early because fpu__init_system() is executed + * before parse_early_param(). + */ +static void __init fpu__init_parse_early_param(void) +{ + /* + * No need to check "eagerfpu=auto" again, since it is the + * initial default. + */ + if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off")) { + eagerfpu = DISABLE; + fpu__clear_eager_fpu_features(); + } else if (cmdline_find_option_bool(boot_command_line, "eagerfpu=on")) { + eagerfpu = ENABLE; + } + + if (cmdline_find_option_bool(boot_command_line, "no387")) + setup_clear_cpu_cap(X86_FEATURE_FPU); + + if (cmdline_find_option_bool(boot_command_line, "nofxsr")) { + setup_clear_cpu_cap(X86_FEATURE_FXSR); + setup_clear_cpu_cap(X86_FEATURE_FXSR_OPT); + setup_clear_cpu_cap(X86_FEATURE_XMM); + } + + if (cmdline_find_option_bool(boot_command_line, "noxsave")) + fpu__xstate_clear_all_cpu_caps(); + + if (cmdline_find_option_bool(boot_command_line, "noxsaveopt")) + setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT); + + if (cmdline_find_option_bool(boot_command_line, "noxsaves")) + setup_clear_cpu_cap(X86_FEATURE_XSAVES); +} + +/* * Called on the boot CPU once per system bootup, to set up the initial * FPU state that is later cloned into all processes: */ void __init fpu__init_system(struct cpuinfo_x86 *c) { + fpu__init_parse_early_param(); fpu__init_system_early_generic(c); /* @@ -344,62 +408,3 @@ void __init fpu__init_system(struct cpuinfo_x86 *c) fpu__init_system_ctx_switch(); } - -/* - * Boot parameter to turn off FPU support and fall back to math-emu: - */ -static int __init no_387(char *s) -{ - setup_clear_cpu_cap(X86_FEATURE_FPU); - return 1; -} -__setup("no387", no_387); - -/* - * Disable all xstate CPU features: - */ -static int __init x86_noxsave_setup(char *s) -{ - if (strlen(s)) - return 0; - - fpu__xstate_clear_all_cpu_caps(); - - return 1; -} -__setup("noxsave", x86_noxsave_setup); - -/* - * Disable the XSAVEOPT instruction specifically: - */ -static int __init x86_noxsaveopt_setup(char *s) -{ - setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT); - - return 1; -} -__setup("noxsaveopt", x86_noxsaveopt_setup); - -/* - * Disable the XSAVES instruction: - */ -static int __init x86_noxsaves_setup(char *s) -{ - setup_clear_cpu_cap(X86_FEATURE_XSAVES); - - return 1; -} -__setup("noxsaves", x86_noxsaves_setup); - -/* - * Disable FX save/restore and SSE support: - */ -static int __init x86_nofxsr_setup(char *s) -{ - setup_clear_cpu_cap(X86_FEATURE_FXSR); - setup_clear_cpu_cap(X86_FEATURE_FXSR_OPT); - setup_clear_cpu_cap(X86_FEATURE_XMM); - - return 1; -} -__setup("nofxsr", x86_nofxsr_setup); |