diff options
Diffstat (limited to 'arch/x86/kernel/fpu/core.c')
-rw-r--r-- | arch/x86/kernel/fpu/core.c | 115 |
1 files changed, 90 insertions, 25 deletions
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index d5804adfa..8e37cc8a5 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -114,6 +114,10 @@ void __kernel_fpu_begin(void) kernel_fpu_disable(); if (fpu->fpregs_active) { + /* + * Ignore return value -- we don't care if reg state + * is clobbered. + */ copy_fpregs_to_fpstate(fpu); } else { this_cpu_write(fpu_fpregs_owner_ctx, NULL); @@ -189,8 +193,12 @@ void fpu__save(struct fpu *fpu) preempt_disable(); if (fpu->fpregs_active) { - if (!copy_fpregs_to_fpstate(fpu)) - fpregs_deactivate(fpu); + if (!copy_fpregs_to_fpstate(fpu)) { + if (use_eager_fpu()) + copy_kernel_to_fpregs(&fpu->state); + else + fpregs_deactivate(fpu); + } } preempt_enable(); } @@ -223,14 +231,15 @@ void fpstate_init(union fpregs_state *state) } EXPORT_SYMBOL_GPL(fpstate_init); -/* - * Copy the current task's FPU state to a new task's FPU context. - * - * In both the 'eager' and the 'lazy' case we save hardware registers - * directly to the destination buffer. - */ -static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu) +int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu) { + dst_fpu->counter = 0; + dst_fpu->fpregs_active = 0; + dst_fpu->last_cpu = -1; + + if (!src_fpu->fpstate_active || !cpu_has_fpu) + return 0; + WARN_ON_FPU(src_fpu != ¤t->thread.fpu); /* @@ -243,10 +252,9 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu) /* * Save current FPU registers directly into the child * FPU context, without any memory-to-memory copying. - * - * If the FPU context got destroyed in the process (FNSAVE - * done on old CPUs) then copy it back into the source - * context and mark the current task for lazy restore. + * In lazy mode, if the FPU context isn't loaded into + * fpregs, CR0.TS will be set and do_device_not_available + * will load the FPU context. * * We have to do all this with preemption disabled, * mostly because of the FNSAVE case, because in that @@ -259,19 +267,13 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu) preempt_disable(); if (!copy_fpregs_to_fpstate(dst_fpu)) { memcpy(&src_fpu->state, &dst_fpu->state, xstate_size); - fpregs_deactivate(src_fpu); + + if (use_eager_fpu()) + copy_kernel_to_fpregs(&src_fpu->state); + else + fpregs_deactivate(src_fpu); } preempt_enable(); -} - -int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu) -{ - dst_fpu->counter = 0; - dst_fpu->fpregs_active = 0; - dst_fpu->last_cpu = -1; - - if (src_fpu->fpstate_active && cpu_has_fpu) - fpu_copy(dst_fpu, src_fpu); return 0; } @@ -352,6 +354,69 @@ void fpu__activate_fpstate_write(struct fpu *fpu) } /* + * This function must be called before we write the current + * task's fpstate. + * + * This call gets the current FPU register state and moves + * it in to the 'fpstate'. Preemption is disabled so that + * no writes to the 'fpstate' can occur from context + * swiches. + * + * Must be followed by a fpu__current_fpstate_write_end(). + */ +void fpu__current_fpstate_write_begin(void) +{ + struct fpu *fpu = ¤t->thread.fpu; + + /* + * Ensure that the context-switching code does not write + * over the fpstate while we are doing our update. + */ + preempt_disable(); + + /* + * Move the fpregs in to the fpu's 'fpstate'. + */ + fpu__activate_fpstate_read(fpu); + + /* + * The caller is about to write to 'fpu'. Ensure that no + * CPU thinks that its fpregs match the fpstate. This + * ensures we will not be lazy and skip a XRSTOR in the + * future. + */ + fpu->last_cpu = -1; +} + +/* + * This function must be paired with fpu__current_fpstate_write_begin() + * + * This will ensure that the modified fpstate gets placed back in + * the fpregs if necessary. + * + * Note: This function may be called whether or not an _actual_ + * write to the fpstate occurred. + */ +void fpu__current_fpstate_write_end(void) +{ + struct fpu *fpu = ¤t->thread.fpu; + + /* + * 'fpu' now has an updated copy of the state, but the + * registers may still be out of date. Update them with + * an XRSTOR if they are active. + */ + if (fpregs_active()) + copy_kernel_to_fpregs(&fpu->state); + + /* + * Our update is done and the fpregs/fpstate are in sync + * if necessary. Context switches can happen again. + */ + preempt_enable(); +} + +/* * 'fpu__restore()' is called to copy FPU registers from * the FPU fpstate to the live hw registers and to activate * access to the hardware registers, so that FPU instructions @@ -425,7 +490,7 @@ void fpu__clear(struct fpu *fpu) { WARN_ON_FPU(fpu != ¤t->thread.fpu); /* Almost certainly an anomaly */ - if (!use_eager_fpu()) { + if (!use_eager_fpu() || !static_cpu_has(X86_FEATURE_FPU)) { /* FPU state will be reallocated lazily at the first use. */ fpu__drop(fpu); } else { |