diff options
Diffstat (limited to 'arch/arm64/kernel/fpsimd.c')
-rw-r--r-- | arch/arm64/kernel/fpsimd.c | 168 |
1 files changed, 111 insertions, 57 deletions
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 0cfcf5c237c5..37d3912cfe06 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -82,7 +82,8 @@ * To prevent this from racing with the manipulation of the task's FPSIMD state * from task context and thereby corrupting the state, it is necessary to * protect any manipulation of a task's fpsimd_state or TIF_FOREIGN_FPSTATE - * flag with local_bh_disable() unless softirqs are already masked. + * flag with {, __}get_cpu_fpsimd_context(). This will still allow softirqs to + * run but prevent them to use FPSIMD. * * For a certain task, the sequence may look something like this: * - the task gets scheduled in; if both the task's fpsimd_cpu field @@ -145,6 +146,56 @@ extern void __percpu *efi_sve_state; #endif /* ! CONFIG_ARM64_SVE */ +DEFINE_PER_CPU(bool, fpsimd_context_busy); +EXPORT_PER_CPU_SYMBOL(fpsimd_context_busy); + +static void __get_cpu_fpsimd_context(void) +{ + bool busy = __this_cpu_xchg(fpsimd_context_busy, true); + + WARN_ON(busy); +} + +/* + * Claim ownership of the CPU FPSIMD context for use by the calling context. + * + * The caller may freely manipulate the FPSIMD context metadata until + * put_cpu_fpsimd_context() is called. + * + * The double-underscore version must only be called if you know the task + * can't be preempted. + */ +static void get_cpu_fpsimd_context(void) +{ + preempt_disable(); + __get_cpu_fpsimd_context(); +} + +static void __put_cpu_fpsimd_context(void) +{ + bool busy = __this_cpu_xchg(fpsimd_context_busy, false); + + WARN_ON(!busy); /* No matching get_cpu_fpsimd_context()? */ +} + +/* + * Release the CPU FPSIMD context. + * + * Must be called from a context in which get_cpu_fpsimd_context() was + * previously called, with no call to put_cpu_fpsimd_context() in the + * meantime. + */ +static void put_cpu_fpsimd_context(void) +{ + __put_cpu_fpsimd_context(); + preempt_enable(); +} + +static bool have_cpu_fpsimd_context(void) +{ + return !preemptible() && __this_cpu_read(fpsimd_context_busy); +} + /* * Call __sve_free() directly only if you know task can't be scheduled * or preempted. @@ -215,12 +266,10 @@ static void sve_free(struct task_struct *task) * This function should be called only when the FPSIMD/SVE state in * thread_struct is known to be up to date, when preparing to enter * userspace. - * - * Softirqs (and preemption) must be disabled. */ static void task_fpsimd_load(void) { - WARN_ON(!in_softirq() && !irqs_disabled()); + WARN_ON(!have_cpu_fpsimd_context()); if (system_supports_sve() && test_thread_flag(TIF_SVE)) sve_load_state(sve_pffr(¤t->thread), @@ -233,16 +282,14 @@ static void task_fpsimd_load(void) /* * Ensure FPSIMD/SVE storage in memory for the loaded context is up to * date with respect to the CPU registers. - * - * Softirqs (and preemption) must be disabled. */ -void fpsimd_save(void) +static void fpsimd_save(void) { struct fpsimd_last_state_struct const *last = this_cpu_ptr(&fpsimd_last_state); /* set by fpsimd_bind_task_to_cpu() or fpsimd_bind_state_to_cpu() */ - WARN_ON(!in_softirq() && !irqs_disabled()); + WARN_ON(!have_cpu_fpsimd_context()); if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) { if (system_supports_sve() && test_thread_flag(TIF_SVE)) { @@ -359,12 +406,25 @@ static __uint128_t arm64_cpu_to_le128(__uint128_t x) #define arm64_le128_to_cpu(x) arm64_cpu_to_le128(x) +static void __fpsimd_to_sve(void *sst, struct user_fpsimd_state const *fst, + unsigned int vq) +{ + unsigned int i; + __uint128_t *p; + + for (i = 0; i < SVE_NUM_ZREGS; ++i) { + p = (__uint128_t *)ZREG(sst, vq, i); + *p = arm64_cpu_to_le128(fst->vregs[i]); + } +} + /* * Transfer the FPSIMD state in task->thread.uw.fpsimd_state to * task->thread.sve_state. * * Task can be a non-runnable task, or current. In the latter case, - * softirqs (and preemption) must be disabled. + * the caller must have ownership of the cpu FPSIMD context before calling + * this function. * task->thread.sve_state must point to at least sve_state_size(task) * bytes of allocated kernel memory. * task->thread.uw.fpsimd_state must be up to date before calling this @@ -375,17 +435,12 @@ static void fpsimd_to_sve(struct task_struct *task) unsigned int vq; void *sst = task->thread.sve_state; struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state; - unsigned int i; - __uint128_t *p; if (!system_supports_sve()) return; vq = sve_vq_from_vl(task->thread.sve_vl); - for (i = 0; i < 32; ++i) { - p = (__uint128_t *)ZREG(sst, vq, i); - *p = arm64_cpu_to_le128(fst->vregs[i]); - } + __fpsimd_to_sve(sst, fst, vq); } /* @@ -393,7 +448,8 @@ static void fpsimd_to_sve(struct task_struct *task) * task->thread.uw.fpsimd_state. * * Task can be a non-runnable task, or current. In the latter case, - * softirqs (and preemption) must be disabled. + * the caller must have ownership of the cpu FPSIMD context before calling + * this function. * task->thread.sve_state must point to at least sve_state_size(task) * bytes of allocated kernel memory. * task->thread.sve_state must be up to date before calling this function. @@ -410,7 +466,7 @@ static void sve_to_fpsimd(struct task_struct *task) return; vq = sve_vq_from_vl(task->thread.sve_vl); - for (i = 0; i < 32; ++i) { + for (i = 0; i < SVE_NUM_ZREGS; ++i) { p = (__uint128_t const *)ZREG(sst, vq, i); fst->vregs[i] = arm64_le128_to_cpu(*p); } @@ -501,8 +557,6 @@ void sve_sync_from_fpsimd_zeropad(struct task_struct *task) unsigned int vq; void *sst = task->thread.sve_state; struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state; - unsigned int i; - __uint128_t *p; if (!test_tsk_thread_flag(task, TIF_SVE)) return; @@ -510,11 +564,7 @@ void sve_sync_from_fpsimd_zeropad(struct task_struct *task) vq = sve_vq_from_vl(task->thread.sve_vl); memset(sst, 0, SVE_SIG_REGS_SIZE(vq)); - - for (i = 0; i < 32; ++i) { - p = (__uint128_t *)ZREG(sst, vq, i); - *p = arm64_cpu_to_le128(fst->vregs[i]); - } + __fpsimd_to_sve(sst, fst, vq); } int sve_set_vector_length(struct task_struct *task, @@ -557,7 +607,7 @@ int sve_set_vector_length(struct task_struct *task, * non-SVE thread. */ if (task == current) { - local_bh_disable(); + get_cpu_fpsimd_context(); fpsimd_save(); } @@ -567,7 +617,7 @@ int sve_set_vector_length(struct task_struct *task, sve_to_fpsimd(task); if (task == current) - local_bh_enable(); + put_cpu_fpsimd_context(); /* * Force reallocation of task SVE state to the correct size @@ -880,7 +930,7 @@ asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs) sve_alloc(current); - local_bh_disable(); + get_cpu_fpsimd_context(); fpsimd_save(); @@ -891,7 +941,7 @@ asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs) if (test_and_set_thread_flag(TIF_SVE)) WARN_ON(1); /* SVE access shouldn't have trapped */ - local_bh_enable(); + put_cpu_fpsimd_context(); } /* @@ -935,6 +985,8 @@ void fpsimd_thread_switch(struct task_struct *next) if (!system_supports_fpsimd()) return; + __get_cpu_fpsimd_context(); + /* Save unsaved fpsimd state, if any: */ fpsimd_save(); @@ -949,6 +1001,8 @@ void fpsimd_thread_switch(struct task_struct *next) update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE, wrong_task || wrong_cpu); + + __put_cpu_fpsimd_context(); } void fpsimd_flush_thread(void) @@ -958,7 +1012,7 @@ void fpsimd_flush_thread(void) if (!system_supports_fpsimd()) return; - local_bh_disable(); + get_cpu_fpsimd_context(); fpsimd_flush_task_state(current); memset(¤t->thread.uw.fpsimd_state, 0, @@ -999,7 +1053,7 @@ void fpsimd_flush_thread(void) current->thread.sve_vl_onexec = 0; } - local_bh_enable(); + put_cpu_fpsimd_context(); } /* @@ -1011,9 +1065,9 @@ void fpsimd_preserve_current_state(void) if (!system_supports_fpsimd()) return; - local_bh_disable(); + get_cpu_fpsimd_context(); fpsimd_save(); - local_bh_enable(); + put_cpu_fpsimd_context(); } /* @@ -1030,7 +1084,8 @@ void fpsimd_signal_preserve_current_state(void) /* * Associate current's FPSIMD context with this cpu - * Preemption must be disabled when calling this function. + * The caller must have ownership of the cpu FPSIMD context before calling + * this function. */ void fpsimd_bind_task_to_cpu(void) { @@ -1076,14 +1131,14 @@ void fpsimd_restore_current_state(void) if (!system_supports_fpsimd()) return; - local_bh_disable(); + get_cpu_fpsimd_context(); if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) { task_fpsimd_load(); fpsimd_bind_task_to_cpu(); } - local_bh_enable(); + put_cpu_fpsimd_context(); } /* @@ -1096,7 +1151,7 @@ void fpsimd_update_current_state(struct user_fpsimd_state const *state) if (!system_supports_fpsimd()) return; - local_bh_disable(); + get_cpu_fpsimd_context(); current->thread.uw.fpsimd_state = *state; if (system_supports_sve() && test_thread_flag(TIF_SVE)) @@ -1107,7 +1162,7 @@ void fpsimd_update_current_state(struct user_fpsimd_state const *state) clear_thread_flag(TIF_FOREIGN_FPSTATE); - local_bh_enable(); + put_cpu_fpsimd_context(); } /* @@ -1133,18 +1188,29 @@ void fpsimd_flush_task_state(struct task_struct *t) /* * Invalidate any task's FPSIMD state that is present on this cpu. - * This function must be called with softirqs disabled. + * The FPSIMD context should be acquired with get_cpu_fpsimd_context() + * before calling this function. */ -void fpsimd_flush_cpu_state(void) +static void fpsimd_flush_cpu_state(void) { __this_cpu_write(fpsimd_last_state.st, NULL); set_thread_flag(TIF_FOREIGN_FPSTATE); } -#ifdef CONFIG_KERNEL_MODE_NEON +/* + * Save the FPSIMD state to memory and invalidate cpu view. + * This function must be called with preemption disabled. + */ +void fpsimd_save_and_flush_cpu_state(void) +{ + WARN_ON(preemptible()); + __get_cpu_fpsimd_context(); + fpsimd_save(); + fpsimd_flush_cpu_state(); + __put_cpu_fpsimd_context(); +} -DEFINE_PER_CPU(bool, kernel_neon_busy); -EXPORT_PER_CPU_SYMBOL(kernel_neon_busy); +#ifdef CONFIG_KERNEL_MODE_NEON /* * Kernel-side NEON support functions @@ -1170,19 +1236,13 @@ void kernel_neon_begin(void) BUG_ON(!may_use_simd()); - local_bh_disable(); - - __this_cpu_write(kernel_neon_busy, true); + get_cpu_fpsimd_context(); /* Save unsaved fpsimd state, if any: */ fpsimd_save(); /* Invalidate any task state remaining in the fpsimd regs: */ fpsimd_flush_cpu_state(); - - preempt_disable(); - - local_bh_enable(); } EXPORT_SYMBOL(kernel_neon_begin); @@ -1197,15 +1257,10 @@ EXPORT_SYMBOL(kernel_neon_begin); */ void kernel_neon_end(void) { - bool busy; - if (!system_supports_fpsimd()) return; - busy = __this_cpu_xchg(kernel_neon_busy, false); - WARN_ON(!busy); /* No matching kernel_neon_begin()? */ - - preempt_enable(); + put_cpu_fpsimd_context(); } EXPORT_SYMBOL(kernel_neon_end); @@ -1297,8 +1352,7 @@ static int fpsimd_cpu_pm_notifier(struct notifier_block *self, { switch (cmd) { case CPU_PM_ENTER: - fpsimd_save(); - fpsimd_flush_cpu_state(); + fpsimd_save_and_flush_cpu_state(); break; case CPU_PM_EXIT: break; |