diff options
| -rw-r--r-- | arch/arm64/include/asm/processor.h | 2 | ||||
| -rw-r--r-- | arch/arm64/include/asm/thread_info.h | 1 | ||||
| -rw-r--r-- | arch/arm64/kernel/fpsimd.c | 92 |
3 files changed, 77 insertions, 18 deletions
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index e5bc54522e71..ce6eebd6c08b 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -167,6 +167,8 @@ struct thread_struct { unsigned long fault_address; /* fault info */ unsigned long fault_code; /* ESR_EL1 value */ struct debug_info debug; /* debugging */ + + struct user_fpsimd_state kernel_fpsimd_state; #ifdef CONFIG_ARM64_PTR_AUTH struct ptrauth_keys_user keys_user; #ifdef CONFIG_ARM64_PTR_AUTH_KERNEL diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 553d1bc559c6..e72a3bf9e563 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -80,6 +80,7 @@ void arch_setup_new_exec(void); #define TIF_TAGGED_ADDR 26 /* Allow tagged user addresses */ #define TIF_SME 27 /* SME in use */ #define TIF_SME_VL_INHERIT 28 /* Inherit SME vl_onexec across exec */ +#define TIF_KERNEL_FPSTATE 29 /* Task is in a kernel mode FPSIMD section */ #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 37ee261b117d..e4595a8d731f 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -357,6 +357,7 @@ static void task_fpsimd_load(void) WARN_ON(!system_supports_fpsimd()); WARN_ON(preemptible()); + WARN_ON(test_thread_flag(TIF_KERNEL_FPSTATE)); if (system_supports_sve() || system_supports_sme()) { switch (current->thread.fp_type) { @@ -379,7 +380,7 @@ static void task_fpsimd_load(void) default: /* * This indicates either a bug in - * fpsimd_save() or memory corruption, we + * fpsimd_save_user_state() or memory corruption, we * should always record an explicit format * when we save. We always at least have the * memory allocated for FPSMID registers so @@ -430,7 +431,7 @@ static void task_fpsimd_load(void) * than via current, if we are saving KVM state then it will have * ensured that the type of registers to save is set in last->to_save. */ -static void fpsimd_save(void) +static void fpsimd_save_user_state(void) { struct cpu_fp_state const *last = this_cpu_ptr(&fpsimd_last_state); @@ -861,7 +862,7 @@ int vec_set_vector_length(struct task_struct *task, enum vec_type type, if (task == current) { get_cpu_fpsimd_context(); - fpsimd_save(); + fpsimd_save_user_state(); } fpsimd_flush_task_state(task); @@ -1473,6 +1474,16 @@ void do_fpsimd_exc(unsigned long esr, struct pt_regs *regs) current); } +static void fpsimd_load_kernel_state(struct task_struct *task) +{ + fpsimd_load_state(&task->thread.kernel_fpsimd_state); +} + +static void fpsimd_save_kernel_state(struct task_struct *task) +{ + fpsimd_save_state(&task->thread.kernel_fpsimd_state); +} + void fpsimd_thread_switch(struct task_struct *next) { bool wrong_task, wrong_cpu; @@ -1483,19 +1494,28 @@ void fpsimd_thread_switch(struct task_struct *next) WARN_ON_ONCE(!irqs_disabled()); /* Save unsaved fpsimd state, if any: */ - fpsimd_save(); + if (test_thread_flag(TIF_KERNEL_FPSTATE)) + fpsimd_save_kernel_state(current); + else + fpsimd_save_user_state(); - /* - * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's - * state. For kernel threads, FPSIMD registers are never loaded - * and wrong_task and wrong_cpu will always be true. - */ - wrong_task = __this_cpu_read(fpsimd_last_state.st) != - &next->thread.uw.fpsimd_state; - wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id(); + if (test_tsk_thread_flag(next, TIF_KERNEL_FPSTATE)) { + fpsimd_load_kernel_state(next); + set_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE); + } else { + /* + * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's + * state. For kernel threads, FPSIMD registers are never + * loaded with user mode FPSIMD state and so wrong_task and + * wrong_cpu will always be true. + */ + wrong_task = __this_cpu_read(fpsimd_last_state.st) != + &next->thread.uw.fpsimd_state; + wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id(); - update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE, - wrong_task || wrong_cpu); + update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE, + wrong_task || wrong_cpu); + } } static void fpsimd_flush_thread_vl(enum vec_type type) @@ -1585,7 +1605,7 @@ void fpsimd_preserve_current_state(void) return; get_cpu_fpsimd_context(); - fpsimd_save(); + fpsimd_save_user_state(); put_cpu_fpsimd_context(); } @@ -1803,7 +1823,7 @@ void fpsimd_save_and_flush_cpu_state(void) return; WARN_ON(preemptible()); local_irq_save(flags); - fpsimd_save(); + fpsimd_save_user_state(); fpsimd_flush_cpu_state(); local_irq_restore(flags); } @@ -1837,10 +1857,37 @@ void kernel_neon_begin(void) get_cpu_fpsimd_context(); /* Save unsaved fpsimd state, if any: */ - fpsimd_save(); + if (test_thread_flag(TIF_KERNEL_FPSTATE)) { + BUG_ON(IS_ENABLED(CONFIG_PREEMPT_RT) || !in_serving_softirq()); + fpsimd_save_kernel_state(current); + } else { + fpsimd_save_user_state(); + + /* + * Set the thread flag so that the kernel mode FPSIMD state + * will be context switched along with the rest of the task + * state. + * + * On non-PREEMPT_RT, softirqs may interrupt task level kernel + * mode FPSIMD, but the task will not be preemptible so setting + * TIF_KERNEL_FPSTATE for those would be both wrong (as it + * would mark the task context FPSIMD state as requiring a + * context switch) and unnecessary. + * + * On PREEMPT_RT, softirqs are serviced from a separate thread, + * which is scheduled as usual, and this guarantees that these + * softirqs are not interrupting use of the FPSIMD in kernel + * mode in task context. So in this case, setting the flag here + * is always appropriate. + */ + if (IS_ENABLED(CONFIG_PREEMPT_RT) || !in_serving_softirq()) + set_thread_flag(TIF_KERNEL_FPSTATE); + } /* Invalidate any task state remaining in the fpsimd regs: */ fpsimd_flush_cpu_state(); + + put_cpu_fpsimd_context(); } EXPORT_SYMBOL_GPL(kernel_neon_begin); @@ -1858,7 +1905,16 @@ void kernel_neon_end(void) if (!system_supports_fpsimd()) return; - put_cpu_fpsimd_context(); + /* + * If we are returning from a nested use of kernel mode FPSIMD, restore + * the task context kernel mode FPSIMD state. This can only happen when + * running in softirq context on non-PREEMPT_RT. + */ + if (!IS_ENABLED(CONFIG_PREEMPT_RT) && in_serving_softirq() && + test_thread_flag(TIF_KERNEL_FPSTATE)) + fpsimd_load_kernel_state(current); + else + clear_thread_flag(TIF_KERNEL_FPSTATE); } EXPORT_SYMBOL_GPL(kernel_neon_end); |