Commit-ID: 2722146eb78451b30e4717a267a3a2b44e4ad317 Gitweb: https://git.kernel.org/tip/2722146eb78451b30e4717a267a3a2b44e4ad317 Author: Sebastian Andrzej Siewior <bige...@linutronix.de> AuthorDate: Wed, 3 Apr 2019 18:41:36 +0200 Committer: Borislav Petkov <b...@suse.de> CommitDate: Wed, 10 Apr 2019 15:42:40 +0200
x86/fpu: Remove fpu->initialized The struct fpu.initialized member is always set to one for user tasks and zero for kernel tasks. This avoids saving/restoring the FPU registers for kernel threads. The ->initialized = 0 case for user tasks has been removed in previous changes, for instance, by doing an explicit unconditional init at fork() time for FPU-less systems which was otherwise delayed until the emulated opcode. The context switch code (switch_fpu_prepare() + switch_fpu_finish()) can't unconditionally save/restore registers for kernel threads. Not only would it slow down the switch but also load a zeroed xcomp_bv for XSAVES. For kernel_fpu_begin() (+end) the situation is similar: EFI with runtime services uses this before alternatives_patched is true. Which means that this function is used too early and it wasn't the case before. For those two cases, use current->mm to distinguish between user and kernel thread. For kernel_fpu_begin() skip save/restore of the FPU registers. During the context switch into a kernel thread don't do anything. There is no reason to save the FPU state of a kernel thread. The reordering in __switch_to() is important because the current() pointer needs to be valid before switch_fpu_finish() is invoked so ->mm is seen of the new task instead the old one. N.B.: fpu__save() doesn't need to check ->mm because it is called by user tasks only. [ bp: Massage. ] Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de> Signed-off-by: Borislav Petkov <b...@suse.de> Reviewed-by: Dave Hansen <dave.han...@intel.com> Reviewed-by: Thomas Gleixner <t...@linutronix.de> Cc: Andy Lutomirski <l...@kernel.org> Cc: Aubrey Li <aubrey...@intel.com> Cc: Babu Moger <babu.mo...@amd.com> Cc: "Chang S. Bae" <chang.seok....@intel.com> Cc: Dmitry Safonov <d...@arista.com> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: Ingo Molnar <mi...@redhat.com> Cc: Jann Horn <ja...@google.com> Cc: "Jason A. Donenfeld" <ja...@zx2c4.com> Cc: Joerg Roedel <jroe...@suse.de> Cc: kvm ML <k...@vger.kernel.org> Cc: Masami Hiramatsu <mhira...@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> Cc: Nicolai Stange <nsta...@suse.de> Cc: Paolo Bonzini <pbonz...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Radim Krčmář <rkrc...@redhat.com> Cc: Rik van Riel <r...@surriel.com> Cc: Sergey Senozhatsky <sergey.senozhat...@gmail.com> Cc: Will Deacon <will.dea...@arm.com> Cc: x86-ml <x...@kernel.org> Link: https://lkml.kernel.org/r/20190403164156.19645-8-bige...@linutronix.de --- arch/x86/ia32/ia32_signal.c | 17 ++++----- arch/x86/include/asm/fpu/internal.h | 18 +++++----- arch/x86/include/asm/fpu/types.h | 9 ----- arch/x86/include/asm/trace/fpu.h | 5 +-- arch/x86/kernel/fpu/core.c | 70 +++++++++++-------------------------- arch/x86/kernel/fpu/init.c | 2 -- arch/x86/kernel/fpu/regset.c | 19 +++------- arch/x86/kernel/fpu/xstate.c | 2 -- arch/x86/kernel/process_32.c | 4 +-- arch/x86/kernel/process_64.c | 4 +-- arch/x86/kernel/signal.c | 17 ++++----- arch/x86/mm/pkeys.c | 7 +--- 12 files changed, 53 insertions(+), 121 deletions(-) diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c index 321fe5f5d0e9..6eeb3249f22f 100644 --- a/arch/x86/ia32/ia32_signal.c +++ b/arch/x86/ia32/ia32_signal.c @@ -216,8 +216,7 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size, void __user **fpstate) { - struct fpu *fpu = ¤t->thread.fpu; - unsigned long sp; + unsigned long sp, fx_aligned, math_size; /* Default to using normal stack */ sp = regs->sp; @@ -231,15 +230,11 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, ksig->ka.sa.sa_restorer) sp = (unsigned long) ksig->ka.sa.sa_restorer; - if (fpu->initialized) { - unsigned long fx_aligned, math_size; - - sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size); - *fpstate = (struct _fpstate_32 __user *) sp; - if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned, - math_size) < 0) - return (void __user *) -1L; - } + sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size); + *fpstate = (struct _fpstate_32 __user *) sp; + if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned, + math_size) < 0) + return (void __user *) -1L; sp -= frame_size; /* Align the stack pointer according to the i386 ABI, diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 70ecb7c032cb..04042eacc852 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -494,11 +494,14 @@ static inline void fpregs_activate(struct fpu *fpu) * * - switch_fpu_finish() restores the new state as * necessary. + * + * The FPU context is only stored/restored for a user task and + * ->mm is used to distinguish between kernel and user threads. */ static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu) { - if (static_cpu_has(X86_FEATURE_FPU) && old_fpu->initialized) { + if (static_cpu_has(X86_FEATURE_FPU) && current->mm) { if (!copy_fpregs_to_fpstate(old_fpu)) old_fpu->last_cpu = -1; else @@ -506,8 +509,7 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu) /* But leave fpu_fpregs_owner_ctx! */ trace_x86_fpu_regs_deactivated(old_fpu); - } else - old_fpu->last_cpu = -1; + } } /* @@ -520,12 +522,12 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu) */ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu) { - bool preload = static_cpu_has(X86_FEATURE_FPU) && - new_fpu->initialized; + if (static_cpu_has(X86_FEATURE_FPU)) { + if (!fpregs_state_valid(new_fpu, cpu)) { + if (current->mm) + copy_kernel_to_fpregs(&new_fpu->state); + } - if (preload) { - if (!fpregs_state_valid(new_fpu, cpu)) - copy_kernel_to_fpregs(&new_fpu->state); fpregs_activate(new_fpu); } } diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index 2e32e178e064..f098f6cab94b 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -293,15 +293,6 @@ struct fpu { */ unsigned int last_cpu; - /* - * @initialized: - * - * This flag indicates whether this context is initialized: if the task - * is not running then we can restore from this context, if the task - * is running then we should save into this context. - */ - unsigned char initialized; - /* * @avx512_timestamp: * diff --git a/arch/x86/include/asm/trace/fpu.h b/arch/x86/include/asm/trace/fpu.h index 069c04be1507..bd65f6ba950f 100644 --- a/arch/x86/include/asm/trace/fpu.h +++ b/arch/x86/include/asm/trace/fpu.h @@ -13,22 +13,19 @@ DECLARE_EVENT_CLASS(x86_fpu, TP_STRUCT__entry( __field(struct fpu *, fpu) - __field(bool, initialized) __field(u64, xfeatures) __field(u64, xcomp_bv) ), TP_fast_assign( __entry->fpu = fpu; - __entry->initialized = fpu->initialized; if (boot_cpu_has(X86_FEATURE_OSXSAVE)) { __entry->xfeatures = fpu->state.xsave.header.xfeatures; __entry->xcomp_bv = fpu->state.xsave.header.xcomp_bv; } ), - TP_printk("x86/fpu: %p initialized: %d xfeatures: %llx xcomp_bv: %llx", + TP_printk("x86/fpu: %p xfeatures: %llx xcomp_bv: %llx", __entry->fpu, - __entry->initialized, __entry->xfeatures, __entry->xcomp_bv ) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index e43296854e37..97e27de2b7c0 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -101,7 +101,7 @@ static void __kernel_fpu_begin(void) kernel_fpu_disable(); - if (fpu->initialized) { + if (current->mm) { /* * Ignore return value -- we don't care if reg state * is clobbered. @@ -116,7 +116,7 @@ static void __kernel_fpu_end(void) { struct fpu *fpu = ¤t->thread.fpu; - if (fpu->initialized) + if (current->mm) copy_kernel_to_fpregs(&fpu->state); kernel_fpu_enable(); @@ -147,11 +147,10 @@ void fpu__save(struct fpu *fpu) preempt_disable(); trace_x86_fpu_before_save(fpu); - if (fpu->initialized) { - if (!copy_fpregs_to_fpstate(fpu)) { - copy_kernel_to_fpregs(&fpu->state); - } - } + + if (!copy_fpregs_to_fpstate(fpu)) + copy_kernel_to_fpregs(&fpu->state); + trace_x86_fpu_after_save(fpu); preempt_enable(); } @@ -190,7 +189,7 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu) { dst_fpu->last_cpu = -1; - if (!src_fpu->initialized || !static_cpu_has(X86_FEATURE_FPU)) + if (!static_cpu_has(X86_FEATURE_FPU)) return 0; WARN_ON_FPU(src_fpu != ¤t->thread.fpu); @@ -227,14 +226,10 @@ static void fpu__initialize(struct fpu *fpu) { WARN_ON_FPU(fpu != ¤t->thread.fpu); - if (!fpu->initialized) { - fpstate_init(&fpu->state); - trace_x86_fpu_init_state(fpu); + fpstate_init(&fpu->state); + trace_x86_fpu_init_state(fpu); - trace_x86_fpu_activate_state(fpu); - /* Safe to do for the current task: */ - fpu->initialized = 1; - } + trace_x86_fpu_activate_state(fpu); } /* @@ -247,32 +242,20 @@ static void fpu__initialize(struct fpu *fpu) * * - or it's called for stopped tasks (ptrace), in which case the * registers were already saved by the context-switch code when - * the task scheduled out - we only have to initialize the registers - * if they've never been initialized. + * the task scheduled out. * * If the task has used the FPU before then save it. */ void fpu__prepare_read(struct fpu *fpu) { - if (fpu == ¤t->thread.fpu) { + if (fpu == ¤t->thread.fpu) fpu__save(fpu); - } else { - if (!fpu->initialized) { - fpstate_init(&fpu->state); - trace_x86_fpu_init_state(fpu); - - trace_x86_fpu_activate_state(fpu); - /* Safe to do for current and for stopped child tasks: */ - fpu->initialized = 1; - } - } } /* * This function must be called before we write a task's fpstate. * - * If the task has used the FPU before then invalidate any cached FPU registers. - * If the task has not used the FPU before then initialize its fpstate. + * Invalidate any cached FPU registers. * * After this function call, after registers in the fpstate are * modified and the child task has woken up, the child task will @@ -289,17 +272,8 @@ void fpu__prepare_write(struct fpu *fpu) */ WARN_ON_FPU(fpu == ¤t->thread.fpu); - if (fpu->initialized) { - /* Invalidate any cached state: */ - __fpu_invalidate_fpregs_state(fpu); - } else { - fpstate_init(&fpu->state); - trace_x86_fpu_init_state(fpu); - - trace_x86_fpu_activate_state(fpu); - /* Safe to do for stopped child tasks: */ - fpu->initialized = 1; - } + /* Invalidate any cached state: */ + __fpu_invalidate_fpregs_state(fpu); } /* @@ -316,17 +290,13 @@ void fpu__drop(struct fpu *fpu) preempt_disable(); if (fpu == ¤t->thread.fpu) { - if (fpu->initialized) { - /* Ignore delayed exceptions from user space */ - asm volatile("1: fwait\n" - "2:\n" - _ASM_EXTABLE(1b, 2b)); - fpregs_deactivate(fpu); - } + /* Ignore delayed exceptions from user space */ + asm volatile("1: fwait\n" + "2:\n" + _ASM_EXTABLE(1b, 2b)); + fpregs_deactivate(fpu); } - fpu->initialized = 0; - trace_x86_fpu_dropped(fpu); preempt_enable(); diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index 6abd83572b01..20d8fa7124c7 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -239,8 +239,6 @@ static void __init fpu__init_system_ctx_switch(void) WARN_ON_FPU(!on_boot_cpu); on_boot_cpu = 0; - - WARN_ON_FPU(current->thread.fpu.initialized); } /* diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 5dbc099178a8..d652b939ccfb 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -15,16 +15,12 @@ */ int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset) { - struct fpu *target_fpu = &target->thread.fpu; - - return target_fpu->initialized ? regset->n : 0; + return regset->n; } int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset) { - struct fpu *target_fpu = &target->thread.fpu; - - if (boot_cpu_has(X86_FEATURE_FXSR) && target_fpu->initialized) + if (boot_cpu_has(X86_FEATURE_FXSR)) return regset->n; else return 0; @@ -370,16 +366,9 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu) { struct task_struct *tsk = current; - struct fpu *fpu = &tsk->thread.fpu; - int fpvalid; - - fpvalid = fpu->initialized; - if (fpvalid) - fpvalid = !fpregs_get(tsk, NULL, - 0, sizeof(struct user_i387_ia32_struct), - ufpu, NULL); - return fpvalid; + return !fpregs_get(tsk, NULL, 0, sizeof(struct user_i387_ia32_struct), + ufpu, NULL); } EXPORT_SYMBOL(dump_fpu); diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index d7432c2b1051..8bfcc5b9e04b 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -892,8 +892,6 @@ const void *get_xsave_field_ptr(int xsave_state) { struct fpu *fpu = ¤t->thread.fpu; - if (!fpu->initialized) - return NULL; /* * fpu__save() takes the CPU's xstate registers * and saves them off to the 'fpu memory buffer. diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 7888a41a03cd..77d9eb43ccac 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -288,10 +288,10 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) if (prev->gs | next->gs) lazy_load_gs(next->gs); - switch_fpu_finish(next_fpu, cpu); - this_cpu_write(current_task, next_p); + switch_fpu_finish(next_fpu, cpu); + /* Load the Intel cache allocation PQR MSR. */ resctrl_sched_in(); diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index e1983b3a16c4..ffea7c557963 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -566,14 +566,14 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) x86_fsgsbase_load(prev, next); - switch_fpu_finish(next_fpu, cpu); - /* * Switch the PDA and FPU contexts. */ this_cpu_write(current_task, next_p); this_cpu_write(cpu_current_top_of_stack, task_top_of_stack(next_p)); + switch_fpu_finish(next_fpu, cpu); + /* Reload sp0. */ update_task_stack(next_p); diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index b419e1a1a0ce..87b327c6cb10 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -246,7 +246,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, unsigned long sp = regs->sp; unsigned long buf_fx = 0; int onsigstack = on_sig_stack(sp); - struct fpu *fpu = ¤t->thread.fpu; + int ret; /* redzone */ if (IS_ENABLED(CONFIG_X86_64)) @@ -265,11 +265,9 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, sp = (unsigned long) ka->sa.sa_restorer; } - if (fpu->initialized) { - sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32), - &buf_fx, &math_size); - *fpstate = (void __user *)sp; - } + sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32), + &buf_fx, &math_size); + *fpstate = (void __user *)sp; sp = align_sigframe(sp - frame_size); @@ -281,8 +279,8 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, return (void __user *)-1L; /* save i387 and extended state */ - if (fpu->initialized && - copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0) + ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size); + if (ret < 0) return (void __user *)-1L; return (void __user *)sp; @@ -763,8 +761,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs) /* * Ensure the signal handler starts with the new fpu state. */ - if (fpu->initialized) - fpu__clear(fpu); + fpu__clear(fpu); } signal_setup_done(failed, ksig, stepping); } diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c index 047a77f6a10c..05bb9a44eb1c 100644 --- a/arch/x86/mm/pkeys.c +++ b/arch/x86/mm/pkeys.c @@ -39,17 +39,12 @@ int __execute_only_pkey(struct mm_struct *mm) * dance to set PKRU if we do not need to. Check it * first and assume that if the execute-only pkey is * write-disabled that we do not have to set it - * ourselves. We need preempt off so that nobody - * can make fpregs inactive. + * ourselves. */ - preempt_disable(); if (!need_to_set_mm_pkey && - current->thread.fpu.initialized && !__pkru_allows_read(read_pkru(), execute_only_pkey)) { - preempt_enable(); return execute_only_pkey; } - preempt_enable(); /* * Set up PKRU so that it denies access for everything
