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- /*
- * xsave/xrstor support.
- *
- * Author: Suresh Siddha <suresh.b.siddha@intel.com>
- */
- #include <linux/compat.h>
- #include <linux/cpu.h>
- #include <asm/fpu/api.h>
- #include <asm/fpu/internal.h>
- #include <asm/fpu/signal.h>
- #include <asm/fpu/regset.h>
- #include <asm/tlbflush.h>
- static const char *xfeature_names[] =
- {
- "x87 floating point registers" ,
- "SSE registers" ,
- "AVX registers" ,
- "MPX bounds registers" ,
- "MPX CSR" ,
- "AVX-512 opmask" ,
- "AVX-512 Hi256" ,
- "AVX-512 ZMM_Hi256" ,
- "unknown xstate feature" ,
- };
- /*
- * Mask of xstate features supported by the CPU and the kernel:
- */
- u64 xfeatures_mask __read_mostly;
- static unsigned int xstate_offsets[XFEATURES_NR_MAX] = { [ 0 ... XFEATURES_NR_MAX - 1] = -1};
- static unsigned int xstate_sizes[XFEATURES_NR_MAX] = { [ 0 ... XFEATURES_NR_MAX - 1] = -1};
- static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
- /* The number of supported xfeatures in xfeatures_mask: */
- static unsigned int xfeatures_nr;
- /*
- * Return whether the system supports a given xfeature.
- *
- * Also return the name of the (most advanced) feature that the caller requested:
- */
- int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
- {
- u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
- if (unlikely(feature_name)) {
- long xfeature_idx, max_idx;
- u64 xfeatures_print;
- /*
- * So we use FLS here to be able to print the most advanced
- * feature that was requested but is missing. So if a driver
- * asks about "XSTATE_SSE | XSTATE_YMM" we'll print the
- * missing AVX feature - this is the most informative message
- * to users:
- */
- if (xfeatures_missing)
- xfeatures_print = xfeatures_missing;
- else
- xfeatures_print = xfeatures_needed;
- xfeature_idx = fls64(xfeatures_print)-1;
- max_idx = ARRAY_SIZE(xfeature_names)-1;
- xfeature_idx = min(xfeature_idx, max_idx);
- *feature_name = xfeature_names[xfeature_idx];
- }
- if (xfeatures_missing)
- return 0;
- return 1;
- }
- EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
- /*
- * When executing XSAVEOPT (or other optimized XSAVE instructions), if
- * a processor implementation detects that an FPU state component is still
- * (or is again) in its initialized state, it may clear the corresponding
- * bit in the header.xfeatures field, and can skip the writeout of registers
- * to the corresponding memory layout.
- *
- * This means that when the bit is zero, the state component might still contain
- * some previous - non-initialized register state.
- *
- * Before writing xstate information to user-space we sanitize those components,
- * to always ensure that the memory layout of a feature will be in the init state
- * if the corresponding header bit is zero. This is to ensure that user-space doesn't
- * see some stale state in the memory layout during signal handling, debugging etc.
- */
- void fpstate_sanitize_xstate(struct fpu *fpu)
- {
- struct fxregs_state *fx = &fpu->state.fxsave;
- int feature_bit;
- u64 xfeatures;
- if (!use_xsaveopt())
- return;
- xfeatures = fpu->state.xsave.header.xfeatures;
- /*
- * None of the feature bits are in init state. So nothing else
- * to do for us, as the memory layout is up to date.
- */
- if ((xfeatures & xfeatures_mask) == xfeatures_mask)
- return;
- /*
- * FP is in init state
- */
- if (!(xfeatures & XSTATE_FP)) {
- fx->cwd = 0x37f;
- fx->swd = 0;
- fx->twd = 0;
- fx->fop = 0;
- fx->rip = 0;
- fx->rdp = 0;
- memset(&fx->st_space[0], 0, 128);
- }
- /*
- * SSE is in init state
- */
- if (!(xfeatures & XSTATE_SSE))
- memset(&fx->xmm_space[0], 0, 256);
- /*
- * First two features are FPU and SSE, which above we handled
- * in a special way already:
- */
- feature_bit = 0x2;
- xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
- /*
- * Update all the remaining memory layouts according to their
- * standard xstate layout, if their header bit is in the init
- * state:
- */
- while (xfeatures) {
- if (xfeatures & 0x1) {
- int offset = xstate_offsets[feature_bit];
- int size = xstate_sizes[feature_bit];
- memcpy((void *)fx + offset,
- (void *)&init_fpstate.xsave + offset,
- size);
- }
- xfeatures >>= 1;
- feature_bit++;
- }
- }
- /*
- * Enable the extended processor state save/restore feature.
- * Called once per CPU onlining.
- */
- void fpu__init_cpu_xstate(void)
- {
- if (!cpu_has_xsave || !xfeatures_mask)
- return;
- cr4_set_bits(X86_CR4_OSXSAVE);
- xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
- }
- /*
- * Record the offsets and sizes of various xstates contained
- * in the XSAVE state memory layout.
- *
- * ( Note that certain features might be non-present, for them
- * we'll have 0 offset and 0 size. )
- */
- static void __init setup_xstate_features(void)
- {
- u32 eax, ebx, ecx, edx, leaf;
- xfeatures_nr = fls64(xfeatures_mask);
- for (leaf = 2; leaf < xfeatures_nr; leaf++) {
- cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
- xstate_offsets[leaf] = ebx;
- xstate_sizes[leaf] = eax;
- printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %04x, xstate_sizes[%d]: %04x\n", leaf, ebx, leaf, eax);
- }
- }
- static void __init print_xstate_feature(u64 xstate_mask)
- {
- const char *feature_name;
- if (cpu_has_xfeatures(xstate_mask, &feature_name))
- pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name);
- }
- /*
- * Print out all the supported xstate features:
- */
- static void __init print_xstate_features(void)
- {
- print_xstate_feature(XSTATE_FP);
- print_xstate_feature(XSTATE_SSE);
- print_xstate_feature(XSTATE_YMM);
- print_xstate_feature(XSTATE_BNDREGS);
- print_xstate_feature(XSTATE_BNDCSR);
- print_xstate_feature(XSTATE_OPMASK);
- print_xstate_feature(XSTATE_ZMM_Hi256);
- print_xstate_feature(XSTATE_Hi16_ZMM);
- }
- /*
- * This function sets up offsets and sizes of all extended states in
- * xsave area. This supports both standard format and compacted format
- * of the xsave aread.
- */
- static void __init setup_xstate_comp(void)
- {
- unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
- int i;
- /*
- * The FP xstates and SSE xstates are legacy states. They are always
- * in the fixed offsets in the xsave area in either compacted form
- * or standard form.
- */
- xstate_comp_offsets[0] = 0;
- xstate_comp_offsets[1] = offsetof(struct fxregs_state, xmm_space);
- if (!cpu_has_xsaves) {
- for (i = 2; i < xfeatures_nr; i++) {
- if (test_bit(i, (unsigned long *)&xfeatures_mask)) {
- xstate_comp_offsets[i] = xstate_offsets[i];
- xstate_comp_sizes[i] = xstate_sizes[i];
- }
- }
- return;
- }
- xstate_comp_offsets[2] = FXSAVE_SIZE + XSAVE_HDR_SIZE;
- for (i = 2; i < xfeatures_nr; i++) {
- if (test_bit(i, (unsigned long *)&xfeatures_mask))
- xstate_comp_sizes[i] = xstate_sizes[i];
- else
- xstate_comp_sizes[i] = 0;
- if (i > 2)
- xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
- + xstate_comp_sizes[i-1];
- }
- }
- /*
- * setup the xstate image representing the init state
- */
- static void __init setup_init_fpu_buf(void)
- {
- static int on_boot_cpu = 1;
- WARN_ON_FPU(!on_boot_cpu);
- on_boot_cpu = 0;
- if (!cpu_has_xsave)
- return;
- setup_xstate_features();
- print_xstate_features();
- if (cpu_has_xsaves) {
- init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
- init_fpstate.xsave.header.xfeatures = xfeatures_mask;
- }
- /*
- * Init all the features state with header_bv being 0x0
- */
- copy_kernel_to_xregs_booting(&init_fpstate.xsave);
- /*
- * Dump the init state again. This is to identify the init state
- * of any feature which is not represented by all zero's.
- */
- copy_xregs_to_kernel_booting(&init_fpstate.xsave);
- }
- /*
- * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
- */
- static void __init init_xstate_size(void)
- {
- unsigned int eax, ebx, ecx, edx;
- int i;
- if (!cpu_has_xsaves) {
- cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
- xstate_size = ebx;
- return;
- }
- xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
- for (i = 2; i < 64; i++) {
- if (test_bit(i, (unsigned long *)&xfeatures_mask)) {
- cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
- xstate_size += eax;
- }
- }
- }
- /*
- * Enable and initialize the xsave feature.
- * Called once per system bootup.
- */
- void __init fpu__init_system_xstate(void)
- {
- unsigned int eax, ebx, ecx, edx;
- static int on_boot_cpu = 1;
- WARN_ON_FPU(!on_boot_cpu);
- on_boot_cpu = 0;
- if (!cpu_has_xsave) {
- pr_info("x86/fpu: Legacy x87 FPU detected.\n");
- return;
- }
- if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
- WARN_ON_FPU(1);
- return;
- }
- cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
- xfeatures_mask = eax + ((u64)edx << 32);
- if ((xfeatures_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
- pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
- BUG();
- }
- /* Support only the state known to the OS: */
- xfeatures_mask = xfeatures_mask & XCNTXT_MASK;
- /* Enable xstate instructions to be able to continue with initialization: */
- fpu__init_cpu_xstate();
- /* Recompute the context size for enabled features: */
- init_xstate_size();
- update_regset_xstate_info(xstate_size, xfeatures_mask);
- fpu__init_prepare_fx_sw_frame();
- setup_init_fpu_buf();
- setup_xstate_comp();
- pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is 0x%x bytes, using '%s' format.\n",
- xfeatures_mask,
- xstate_size,
- cpu_has_xsaves ? "compacted" : "standard");
- }
- /*
- * Restore minimal FPU state after suspend:
- */
- void fpu__resume_cpu(void)
- {
- /*
- * Restore XCR0 on xsave capable CPUs:
- */
- if (cpu_has_xsave)
- xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
- }
- /*
- * Given the xsave area and a state inside, this function returns the
- * address of the state.
- *
- * This is the API that is called to get xstate address in either
- * standard format or compacted format of xsave area.
- *
- * Note that if there is no data for the field in the xsave buffer
- * this will return NULL.
- *
- * Inputs:
- * xstate: the thread's storage area for all FPU data
- * xstate_feature: state which is defined in xsave.h (e.g.
- * XSTATE_FP, XSTATE_SSE, etc...)
- * Output:
- * address of the state in the xsave area, or NULL if the
- * field is not present in the xsave buffer.
- */
- void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
- {
- int feature_nr = fls64(xstate_feature) - 1;
- /*
- * Do we even *have* xsave state?
- */
- if (!boot_cpu_has(X86_FEATURE_XSAVE))
- return NULL;
- xsave = ¤t->thread.fpu.state.xsave;
- /*
- * We should not ever be requesting features that we
- * have not enabled. Remember that pcntxt_mask is
- * what we write to the XCR0 register.
- */
- WARN_ONCE(!(xfeatures_mask & xstate_feature),
- "get of unsupported state");
- /*
- * This assumes the last 'xsave*' instruction to
- * have requested that 'xstate_feature' be saved.
- * If it did not, we might be seeing and old value
- * of the field in the buffer.
- *
- * This can happen because the last 'xsave' did not
- * request that this feature be saved (unlikely)
- * or because the "init optimization" caused it
- * to not be saved.
- */
- if (!(xsave->header.xfeatures & xstate_feature))
- return NULL;
- return (void *)xsave + xstate_comp_offsets[feature_nr];
- }
- EXPORT_SYMBOL_GPL(get_xsave_addr);
- /*
- * This wraps up the common operations that need to occur when retrieving
- * data from xsave state. It first ensures that the current task was
- * using the FPU and retrieves the data in to a buffer. It then calculates
- * the offset of the requested field in the buffer.
- *
- * This function is safe to call whether the FPU is in use or not.
- *
- * Note that this only works on the current task.
- *
- * Inputs:
- * @xsave_state: state which is defined in xsave.h (e.g. XSTATE_FP,
- * XSTATE_SSE, etc...)
- * Output:
- * address of the state in the xsave area or NULL if the state
- * is not present or is in its 'init state'.
- */
- const void *get_xsave_field_ptr(int xsave_state)
- {
- struct fpu *fpu = ¤t->thread.fpu;
- if (!fpu->fpstate_active)
- return NULL;
- /*
- * fpu__save() takes the CPU's xstate registers
- * and saves them off to the 'fpu memory buffer.
- */
- fpu__save(fpu);
- return get_xsave_addr(&fpu->state.xsave, xsave_state);
- }
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