2 * xsave/xrstor support.
4 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
6 #include <linux/compat.h>
9 #include <asm/fpu/api.h>
10 #include <asm/fpu/internal.h>
11 #include <asm/fpu/signal.h>
12 #include <asm/fpu/regset.h>
14 #include <asm/tlbflush.h>
16 static const char *xfeature_names[] =
18 "x87 floating point registers" ,
21 "MPX bounds registers" ,
26 "unknown xstate feature" ,
30 * Mask of xstate features supported by the CPU and the kernel:
32 u64 xfeatures_mask __read_mostly;
34 static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
35 static unsigned int xstate_sizes[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
36 static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
39 * Clear all of the X86_FEATURE_* bits that are unavailable
40 * when the CPU has no XSAVE support.
42 void fpu__xstate_clear_all_cpu_caps(void)
44 setup_clear_cpu_cap(X86_FEATURE_XSAVE);
45 setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
46 setup_clear_cpu_cap(X86_FEATURE_XSAVEC);
47 setup_clear_cpu_cap(X86_FEATURE_XSAVES);
48 setup_clear_cpu_cap(X86_FEATURE_AVX);
49 setup_clear_cpu_cap(X86_FEATURE_AVX2);
50 setup_clear_cpu_cap(X86_FEATURE_AVX512F);
51 setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
52 setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
53 setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
54 setup_clear_cpu_cap(X86_FEATURE_AVX512DQ);
55 setup_clear_cpu_cap(X86_FEATURE_AVX512BW);
56 setup_clear_cpu_cap(X86_FEATURE_AVX512VL);
57 setup_clear_cpu_cap(X86_FEATURE_MPX);
58 setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
62 * Return whether the system supports a given xfeature.
64 * Also return the name of the (most advanced) feature that the caller requested:
66 int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
68 u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
70 if (unlikely(feature_name)) {
71 long xfeature_idx, max_idx;
74 * So we use FLS here to be able to print the most advanced
75 * feature that was requested but is missing. So if a driver
76 * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
77 * missing AVX feature - this is the most informative message
80 if (xfeatures_missing)
81 xfeatures_print = xfeatures_missing;
83 xfeatures_print = xfeatures_needed;
85 xfeature_idx = fls64(xfeatures_print)-1;
86 max_idx = ARRAY_SIZE(xfeature_names)-1;
87 xfeature_idx = min(xfeature_idx, max_idx);
89 *feature_name = xfeature_names[xfeature_idx];
92 if (xfeatures_missing)
97 EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
100 * When executing XSAVEOPT (or other optimized XSAVE instructions), if
101 * a processor implementation detects that an FPU state component is still
102 * (or is again) in its initialized state, it may clear the corresponding
103 * bit in the header.xfeatures field, and can skip the writeout of registers
104 * to the corresponding memory layout.
106 * This means that when the bit is zero, the state component might still contain
107 * some previous - non-initialized register state.
109 * Before writing xstate information to user-space we sanitize those components,
110 * to always ensure that the memory layout of a feature will be in the init state
111 * if the corresponding header bit is zero. This is to ensure that user-space doesn't
112 * see some stale state in the memory layout during signal handling, debugging etc.
114 void fpstate_sanitize_xstate(struct fpu *fpu)
116 struct fxregs_state *fx = &fpu->state.fxsave;
123 xfeatures = fpu->state.xsave.header.xfeatures;
126 * None of the feature bits are in init state. So nothing else
127 * to do for us, as the memory layout is up to date.
129 if ((xfeatures & xfeatures_mask) == xfeatures_mask)
133 * FP is in init state
135 if (!(xfeatures & XFEATURE_MASK_FP)) {
142 memset(&fx->st_space[0], 0, 128);
146 * SSE is in init state
148 if (!(xfeatures & XFEATURE_MASK_SSE))
149 memset(&fx->xmm_space[0], 0, 256);
152 * First two features are FPU and SSE, which above we handled
153 * in a special way already:
156 xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
159 * Update all the remaining memory layouts according to their
160 * standard xstate layout, if their header bit is in the init
164 if (xfeatures & 0x1) {
165 int offset = xstate_offsets[feature_bit];
166 int size = xstate_sizes[feature_bit];
168 memcpy((void *)fx + offset,
169 (void *)&init_fpstate.xsave + offset,
179 * Enable the extended processor state save/restore feature.
180 * Called once per CPU onlining.
182 void fpu__init_cpu_xstate(void)
184 if (!cpu_has_xsave || !xfeatures_mask)
187 cr4_set_bits(X86_CR4_OSXSAVE);
188 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
192 * Note that in the future we will likely need a pair of
193 * functions here: one for user xstates and the other for
194 * system xstates. For now, they are the same.
196 static int xfeature_enabled(enum xfeature xfeature)
198 return !!(xfeatures_mask & (1UL << xfeature));
202 * Record the offsets and sizes of various xstates contained
203 * in the XSAVE state memory layout.
205 static void __init setup_xstate_features(void)
207 u32 eax, ebx, ecx, edx, i;
208 /* start at the beginnning of the "extended state" */
209 unsigned int last_good_offset = offsetof(struct xregs_state,
210 extended_state_area);
212 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
213 if (!xfeature_enabled(i))
216 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
217 xstate_offsets[i] = ebx;
218 xstate_sizes[i] = eax;
220 * In our xstate size checks, we assume that the
221 * highest-numbered xstate feature has the
222 * highest offset in the buffer. Ensure it does.
224 WARN_ONCE(last_good_offset > xstate_offsets[i],
225 "x86/fpu: misordered xstate at %d\n", last_good_offset);
226 last_good_offset = xstate_offsets[i];
228 printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", i, ebx, i, eax);
232 static void __init print_xstate_feature(u64 xstate_mask)
234 const char *feature_name;
236 if (cpu_has_xfeatures(xstate_mask, &feature_name))
237 pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name);
241 * Print out all the supported xstate features:
243 static void __init print_xstate_features(void)
245 print_xstate_feature(XFEATURE_MASK_FP);
246 print_xstate_feature(XFEATURE_MASK_SSE);
247 print_xstate_feature(XFEATURE_MASK_YMM);
248 print_xstate_feature(XFEATURE_MASK_BNDREGS);
249 print_xstate_feature(XFEATURE_MASK_BNDCSR);
250 print_xstate_feature(XFEATURE_MASK_OPMASK);
251 print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
252 print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
256 * This function sets up offsets and sizes of all extended states in
257 * xsave area. This supports both standard format and compacted format
258 * of the xsave aread.
260 static void __init setup_xstate_comp(void)
262 unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
266 * The FP xstates and SSE xstates are legacy states. They are always
267 * in the fixed offsets in the xsave area in either compacted form
270 xstate_comp_offsets[0] = 0;
271 xstate_comp_offsets[1] = offsetof(struct fxregs_state, xmm_space);
273 if (!cpu_has_xsaves) {
274 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
275 if (xfeature_enabled(i)) {
276 xstate_comp_offsets[i] = xstate_offsets[i];
277 xstate_comp_sizes[i] = xstate_sizes[i];
283 xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
284 FXSAVE_SIZE + XSAVE_HDR_SIZE;
286 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
287 if (xfeature_enabled(i))
288 xstate_comp_sizes[i] = xstate_sizes[i];
290 xstate_comp_sizes[i] = 0;
292 if (i > FIRST_EXTENDED_XFEATURE)
293 xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
294 + xstate_comp_sizes[i-1];
300 * setup the xstate image representing the init state
302 static void __init setup_init_fpu_buf(void)
304 static int on_boot_cpu __initdata = 1;
306 WARN_ON_FPU(!on_boot_cpu);
312 setup_xstate_features();
313 print_xstate_features();
315 if (cpu_has_xsaves) {
316 init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
317 init_fpstate.xsave.header.xfeatures = xfeatures_mask;
321 * Init all the features state with header_bv being 0x0
323 copy_kernel_to_xregs_booting(&init_fpstate.xsave);
326 * Dump the init state again. This is to identify the init state
327 * of any feature which is not represented by all zero's.
329 copy_xregs_to_kernel_booting(&init_fpstate.xsave);
332 static int xfeature_is_supervisor(int xfeature_nr)
335 * We currently do not support supervisor states, but if
336 * we did, we could find out like this.
338 * SDM says: If state component i is a user state component,
339 * ECX[0] return 0; if state component i is a supervisor
340 * state component, ECX[0] returns 1.
341 u32 eax, ebx, ecx, edx;
342 cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;
348 static int xfeature_is_user(int xfeature_nr)
350 return !xfeature_is_supervisor(xfeature_nr);
355 * This check is important because it is easy to get XSTATE_*
356 * confused with XSTATE_BIT_*.
358 #define CHECK_XFEATURE(nr) do { \
359 WARN_ON(nr < FIRST_EXTENDED_XFEATURE); \
360 WARN_ON(nr >= XFEATURE_MAX); \
364 * We could cache this like xstate_size[], but we only use
365 * it here, so it would be a waste of space.
367 static int xfeature_is_aligned(int xfeature_nr)
369 u32 eax, ebx, ecx, edx;
371 CHECK_XFEATURE(xfeature_nr);
372 cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
374 * The value returned by ECX[1] indicates the alignment
375 * of state component i when the compacted format
376 * of the extended region of an XSAVE area is used
381 static int xfeature_uncompacted_offset(int xfeature_nr)
383 u32 eax, ebx, ecx, edx;
385 CHECK_XFEATURE(xfeature_nr);
386 cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
390 static int xfeature_size(int xfeature_nr)
392 u32 eax, ebx, ecx, edx;
394 CHECK_XFEATURE(xfeature_nr);
395 cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
400 * 'XSAVES' implies two different things:
401 * 1. saving of supervisor/system state
402 * 2. using the compacted format
404 * Use this function when dealing with the compacted format so
405 * that it is obvious which aspect of 'XSAVES' is being handled
406 * by the calling code.
408 static int using_compacted_format(void)
410 return cpu_has_xsaves;
413 static void __xstate_dump_leaves(void)
416 u32 eax, ebx, ecx, edx;
417 static int should_dump = 1;
423 * Dump out a few leaves past the ones that we support
424 * just in case there are some goodies up there
426 for (i = 0; i < XFEATURE_MAX + 10; i++) {
427 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
428 pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
429 XSTATE_CPUID, i, eax, ebx, ecx, edx);
433 #define XSTATE_WARN_ON(x) do { \
434 if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) { \
435 __xstate_dump_leaves(); \
439 #define XCHECK_SZ(sz, nr, nr_macro, __struct) do { \
440 if ((nr == nr_macro) && \
441 WARN_ONCE(sz != sizeof(__struct), \
442 "%s: struct is %zu bytes, cpu state %d bytes\n", \
443 __stringify(nr_macro), sizeof(__struct), sz)) { \
444 __xstate_dump_leaves(); \
449 * We have a C struct for each 'xstate'. We need to ensure
450 * that our software representation matches what the CPU
451 * tells us about the state's size.
453 static void check_xstate_against_struct(int nr)
456 * Ask the CPU for the size of the state.
458 int sz = xfeature_size(nr);
460 * Match each CPU state with the corresponding software
463 XCHECK_SZ(sz, nr, XFEATURE_YMM, struct ymmh_struct);
464 XCHECK_SZ(sz, nr, XFEATURE_BNDREGS, struct mpx_bndreg_state);
465 XCHECK_SZ(sz, nr, XFEATURE_BNDCSR, struct mpx_bndcsr_state);
466 XCHECK_SZ(sz, nr, XFEATURE_OPMASK, struct avx_512_opmask_state);
467 XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
468 XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM, struct avx_512_hi16_state);
471 * Make *SURE* to add any feature numbers in below if
472 * there are "holes" in the xsave state component
475 if ((nr < XFEATURE_YMM) ||
476 (nr >= XFEATURE_MAX)) {
477 WARN_ONCE(1, "no structure for xstate: %d\n", nr);
483 * This essentially double-checks what the cpu told us about
484 * how large the XSAVE buffer needs to be. We are recalculating
487 static void do_extra_xstate_size_checks(void)
489 int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
492 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
493 if (!xfeature_enabled(i))
496 check_xstate_against_struct(i);
498 * Supervisor state components can be managed only by
499 * XSAVES, which is compacted-format only.
501 if (!using_compacted_format())
502 XSTATE_WARN_ON(xfeature_is_supervisor(i));
504 /* Align from the end of the previous feature */
505 if (xfeature_is_aligned(i))
506 paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
508 * The offset of a given state in the non-compacted
509 * format is given to us in a CPUID leaf. We check
510 * them for being ordered (increasing offsets) in
511 * setup_xstate_features().
513 if (!using_compacted_format())
514 paranoid_xstate_size = xfeature_uncompacted_offset(i);
516 * The compacted-format offset always depends on where
517 * the previous state ended.
519 paranoid_xstate_size += xfeature_size(i);
521 XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
525 * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
527 * Note the SDM's wording here. "sub-function 0" only enumerates
528 * the size of the *user* states. If we use it to size a buffer
529 * that we use 'XSAVES' on, we could potentially overflow the
530 * buffer because 'XSAVES' saves system states too.
532 * Note that we do not currently set any bits on IA32_XSS so
533 * 'XCR0 | IA32_XSS == XCR0' for now.
535 static unsigned int __init calculate_xstate_size(void)
537 unsigned int eax, ebx, ecx, edx;
538 unsigned int calculated_xstate_size;
540 if (!cpu_has_xsaves) {
542 * - CPUID function 0DH, sub-function 0:
543 * EBX enumerates the size (in bytes) required by
544 * the XSAVE instruction for an XSAVE area
545 * containing all the *user* state components
546 * corresponding to bits currently set in XCR0.
548 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
549 calculated_xstate_size = ebx;
552 * - CPUID function 0DH, sub-function 1:
553 * EBX enumerates the size (in bytes) required by
554 * the XSAVES instruction for an XSAVE area
555 * containing all the state components
556 * corresponding to bits currently set in
559 cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
560 calculated_xstate_size = ebx;
562 return calculated_xstate_size;
566 * Will the runtime-enumerated 'xstate_size' fit in the init
567 * task's statically-allocated buffer?
569 static bool is_supported_xstate_size(unsigned int test_xstate_size)
571 if (test_xstate_size <= sizeof(union fpregs_state))
574 pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
575 sizeof(union fpregs_state), test_xstate_size);
579 static int init_xstate_size(void)
581 /* Recompute the context size for enabled features: */
582 unsigned int possible_xstate_size = calculate_xstate_size();
584 /* Ensure we have the space to store all enabled: */
585 if (!is_supported_xstate_size(possible_xstate_size))
589 * The size is OK, we are definitely going to use xsave,
590 * make it known to the world that we need more space.
592 xstate_size = possible_xstate_size;
593 do_extra_xstate_size_checks();
598 * We enabled the XSAVE hardware, but something went wrong and
599 * we can not use it. Disable it.
601 static void fpu__init_disable_system_xstate(void)
604 cr4_clear_bits(X86_CR4_OSXSAVE);
605 fpu__xstate_clear_all_cpu_caps();
609 * Enable and initialize the xsave feature.
610 * Called once per system bootup.
612 void __init fpu__init_system_xstate(void)
614 unsigned int eax, ebx, ecx, edx;
615 static int on_boot_cpu __initdata = 1;
618 WARN_ON_FPU(!on_boot_cpu);
621 if (!cpu_has_xsave) {
622 pr_info("x86/fpu: Legacy x87 FPU detected.\n");
626 if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
631 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
632 xfeatures_mask = eax + ((u64)edx << 32);
634 if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
635 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
639 xfeatures_mask &= fpu__get_supported_xfeatures_mask();
641 /* Enable xstate instructions to be able to continue with initialization: */
642 fpu__init_cpu_xstate();
643 err = init_xstate_size();
645 /* something went wrong, boot without any XSAVE support */
646 fpu__init_disable_system_xstate();
650 update_regset_xstate_info(xstate_size, xfeatures_mask);
651 fpu__init_prepare_fx_sw_frame();
652 setup_init_fpu_buf();
655 pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
658 cpu_has_xsaves ? "compacted" : "standard");
662 * Restore minimal FPU state after suspend:
664 void fpu__resume_cpu(void)
667 * Restore XCR0 on xsave capable CPUs:
670 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
674 * Given the xsave area and a state inside, this function returns the
675 * address of the state.
677 * This is the API that is called to get xstate address in either
678 * standard format or compacted format of xsave area.
680 * Note that if there is no data for the field in the xsave buffer
681 * this will return NULL.
684 * xstate: the thread's storage area for all FPU data
685 * xstate_feature: state which is defined in xsave.h (e.g.
686 * XFEATURE_MASK_FP, XFEATURE_MASK_SSE, etc...)
688 * address of the state in the xsave area, or NULL if the
689 * field is not present in the xsave buffer.
691 void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
693 int feature_nr = fls64(xstate_feature) - 1;
695 * Do we even *have* xsave state?
697 if (!boot_cpu_has(X86_FEATURE_XSAVE))
701 * We should not ever be requesting features that we
702 * have not enabled. Remember that pcntxt_mask is
703 * what we write to the XCR0 register.
705 WARN_ONCE(!(xfeatures_mask & xstate_feature),
706 "get of unsupported state");
708 * This assumes the last 'xsave*' instruction to
709 * have requested that 'xstate_feature' be saved.
710 * If it did not, we might be seeing and old value
711 * of the field in the buffer.
713 * This can happen because the last 'xsave' did not
714 * request that this feature be saved (unlikely)
715 * or because the "init optimization" caused it
718 if (!(xsave->header.xfeatures & xstate_feature))
721 return (void *)xsave + xstate_comp_offsets[feature_nr];
723 EXPORT_SYMBOL_GPL(get_xsave_addr);
726 * This wraps up the common operations that need to occur when retrieving
727 * data from xsave state. It first ensures that the current task was
728 * using the FPU and retrieves the data in to a buffer. It then calculates
729 * the offset of the requested field in the buffer.
731 * This function is safe to call whether the FPU is in use or not.
733 * Note that this only works on the current task.
736 * @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
737 * XFEATURE_MASK_SSE, etc...)
739 * address of the state in the xsave area or NULL if the state
740 * is not present or is in its 'init state'.
742 const void *get_xsave_field_ptr(int xsave_state)
744 struct fpu *fpu = ¤t->thread.fpu;
746 if (!fpu->fpstate_active)
749 * fpu__save() takes the CPU's xstate registers
750 * and saves them off to the 'fpu memory buffer.
754 return get_xsave_addr(&fpu->state.xsave, xsave_state);