2 * x86 FPU boot time init code:
4 #include <asm/fpu/internal.h>
5 #include <asm/tlbflush.h>
7 #include <asm/cmdline.h>
9 #include <linux/sched.h>
10 #include <linux/init.h>
13 * Initialize the TS bit in CR0 according to the style of context-switches
16 static void fpu__init_cpu_ctx_switch(void)
22 * Initialize the registers found in all CPUs, CR0 and CR4:
24 static void fpu__init_cpu_generic(void)
27 unsigned long cr4_mask = 0;
30 cr4_mask |= X86_CR4_OSFXSR;
32 cr4_mask |= X86_CR4_OSXMMEXCPT;
34 cr4_set_bits(cr4_mask);
37 cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
42 /* Flush out any pending x87 state: */
43 #ifdef CONFIG_MATH_EMULATION
45 fpstate_init_soft(¤t->thread.fpu.state.soft);
48 asm volatile ("fninit");
52 * Enable all supported FPU features. Called when a CPU is brought online:
54 void fpu__init_cpu(void)
56 fpu__init_cpu_generic();
57 fpu__init_cpu_xstate();
58 fpu__init_cpu_ctx_switch();
62 * The earliest FPU detection code.
64 * Set the X86_FEATURE_FPU CPU-capability bit based on
65 * trying to execute an actual sequence of FPU instructions:
67 static void fpu__init_system_early_generic(struct cpuinfo_x86 *c)
75 cr0 &= ~(X86_CR0_TS | X86_CR0_EM);
78 if (!test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) {
79 asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
80 : "+m" (fsw), "+m" (fcw));
82 if (fsw == 0 && (fcw & 0x103f) == 0x003f)
83 set_cpu_cap(c, X86_FEATURE_FPU);
85 clear_cpu_cap(c, X86_FEATURE_FPU);
88 #ifndef CONFIG_MATH_EMULATION
90 pr_emerg("x86/fpu: Giving up, no FPU found and no math emulation present\n");
98 * Boot time FPU feature detection code:
100 unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
101 EXPORT_SYMBOL_GPL(mxcsr_feature_mask);
103 static void __init fpu__init_system_mxcsr(void)
105 unsigned int mask = 0;
108 /* Static because GCC does not get 16-byte stack alignment right: */
109 static struct fxregs_state fxregs __initdata;
111 asm volatile("fxsave %0" : "+m" (fxregs));
113 mask = fxregs.mxcsr_mask;
116 * If zero then use the default features mask,
117 * which has all features set, except the
118 * denormals-are-zero feature bit:
123 mxcsr_feature_mask &= mask;
127 * Once per bootup FPU initialization sequences that will run on most x86 CPUs:
129 static void __init fpu__init_system_generic(void)
132 * Set up the legacy init FPU context. (xstate init might overwrite this
133 * with a more modern format, if the CPU supports it.)
135 fpstate_init(&init_fpstate);
137 fpu__init_system_mxcsr();
141 * Size of the FPU context state. All tasks in the system use the
142 * same context size, regardless of what portion they use.
143 * This is inherent to the XSAVE architecture which puts all state
144 * components into a single, continuous memory block:
146 unsigned int xstate_size;
147 EXPORT_SYMBOL_GPL(xstate_size);
149 /* Enforce that 'MEMBER' is the last field of 'TYPE': */
150 #define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \
151 BUILD_BUG_ON(sizeof(TYPE) != offsetofend(TYPE, MEMBER))
154 * We append the 'struct fpu' to the task_struct:
156 static void __init fpu__init_task_struct_size(void)
158 int task_size = sizeof(struct task_struct);
161 * Subtract off the static size of the register state.
162 * It potentially has a bunch of padding.
164 task_size -= sizeof(((struct task_struct *)0)->thread.fpu.state);
167 * Add back the dynamically-calculated register state
170 task_size += xstate_size;
173 * We dynamically size 'struct fpu', so we require that
174 * it be at the end of 'thread_struct' and that
175 * 'thread_struct' be at the end of 'task_struct'. If
176 * you hit a compile error here, check the structure to
177 * see if something got added to the end.
179 CHECK_MEMBER_AT_END_OF(struct fpu, state);
180 CHECK_MEMBER_AT_END_OF(struct thread_struct, fpu);
181 CHECK_MEMBER_AT_END_OF(struct task_struct, thread);
183 arch_task_struct_size = task_size;
187 * Set up the xstate_size based on the legacy FPU context size.
189 * We set this up first, and later it will be overwritten by
190 * fpu__init_system_xstate() if the CPU knows about xstates.
192 static void __init fpu__init_system_xstate_size_legacy(void)
194 static int on_boot_cpu = 1;
196 WARN_ON_FPU(!on_boot_cpu);
200 * Note that xstate_size might be overwriten later during
201 * fpu__init_system_xstate().
206 * Disable xsave as we do not support it if i387
207 * emulation is enabled.
209 setup_clear_cpu_cap(X86_FEATURE_XSAVE);
210 setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
211 xstate_size = sizeof(struct swregs_state);
214 xstate_size = sizeof(struct fxregs_state);
216 xstate_size = sizeof(struct fregs_state);
219 * Quirk: we don't yet handle the XSAVES* instructions
220 * correctly, as we don't correctly convert between
221 * standard and compacted format when interfacing
222 * with user-space - so disable it for now.
224 * The difference is small: with recent CPUs the
225 * compacted format is only marginally smaller than
226 * the standard FPU state format.
228 * ( This is easy to backport while we are fixing
231 setup_clear_cpu_cap(X86_FEATURE_XSAVES);
235 * Find supported xfeatures based on cpu features and command-line input.
236 * This must be called after fpu__init_parse_early_param() is called and
237 * xfeatures_mask is enumerated.
239 u64 __init fpu__get_supported_xfeatures_mask(void)
244 /* Legacy code to initialize eager fpu mode. */
245 static void __init fpu__init_system_ctx_switch(void)
247 static bool on_boot_cpu = 1;
249 WARN_ON_FPU(!on_boot_cpu);
252 WARN_ON_FPU(current->thread.fpu.fpstate_active);
253 current_thread_info()->status = 0;
257 * We parse fpu parameters early because fpu__init_system() is executed
258 * before parse_early_param().
260 static void __init fpu__init_parse_early_param(void)
262 if (cmdline_find_option_bool(boot_command_line, "no387"))
263 setup_clear_cpu_cap(X86_FEATURE_FPU);
265 if (cmdline_find_option_bool(boot_command_line, "nofxsr")) {
266 setup_clear_cpu_cap(X86_FEATURE_FXSR);
267 setup_clear_cpu_cap(X86_FEATURE_FXSR_OPT);
268 setup_clear_cpu_cap(X86_FEATURE_XMM);
271 if (cmdline_find_option_bool(boot_command_line, "noxsave"))
272 fpu__xstate_clear_all_cpu_caps();
274 if (cmdline_find_option_bool(boot_command_line, "noxsaveopt"))
275 setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
277 if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
278 setup_clear_cpu_cap(X86_FEATURE_XSAVES);
282 * Called on the boot CPU once per system bootup, to set up the initial
283 * FPU state that is later cloned into all processes:
285 void __init fpu__init_system(struct cpuinfo_x86 *c)
287 fpu__init_parse_early_param();
288 fpu__init_system_early_generic(c);
291 * The FPU has to be operational for some of the
292 * later FPU init activities:
297 * But don't leave CR0::TS set yet, as some of the FPU setup
298 * methods depend on being able to execute FPU instructions
299 * that will fault on a set TS, such as the FXSAVE in
300 * fpu__init_system_mxcsr().
304 fpu__init_system_generic();
305 fpu__init_system_xstate_size_legacy();
306 fpu__init_system_xstate();
307 fpu__init_task_struct_size();
309 fpu__init_system_ctx_switch();