Only enable XNFPU on first FPU use in kernel-space.
Skip context restore with fxsr when context allows it.
---
kernel/cobalt/arch/x86/thread.c | 33 ++++++++++++++++++++++++---------
1 file changed, 24 insertions(+), 9 deletions(-)
diff --git a/kernel/cobalt/arch/x86/thread.c b/kernel/cobalt/arch/x86/thread.c
index 2cb5ff1..aa35eb6 100644
--- a/kernel/cobalt/arch/x86/thread.c
+++ b/kernel/cobalt/arch/x86/thread.c
@@ -225,7 +225,7 @@ int xnarch_handle_fpu_fault(struct xnthread *from,
struct xnarchtcb *tcb = xnthread_archtcb(to);
struct task_struct *p = tcb->core.host_task;
- if (tsk_used_math(p))
+ if (wrap_test_fpu_used(p))
return 0;
/*
@@ -243,6 +243,7 @@ int xnarch_handle_fpu_fault(struct xnthread *from,
set_stopped_child_used_math(p);
wrap_set_fpu_used(p);
+ xnthread_set_state(to, XNFPU);
return 1;
}
@@ -273,7 +274,7 @@ void xnarch_save_fpu(struct xnthread *thread)
struct task_struct *p = tcb->core.host_task;
if (wrap_test_fpu_used(p) == 0)
- /* Common case: already saved by __switch_to */
+ /* Saved by last __switch_to */
return;
/* Exceptional case: a migrating thread */
@@ -287,11 +288,28 @@ int xnarch_switch_fpu(struct xnthread *from, struct
xnthread *thread)
{
struct xnarchtcb *tcb = xnthread_archtcb(thread);
struct task_struct *p = tcb->core.host_task;
+ const unsigned root_kfpu = tcb->root_kfpu;
- if (tcb->root_kfpu == 0 &&
- (tsk_used_math(p) == 0 || xnthread_test_state(thread, XNROOT)))
+ if (root_kfpu == 0) {
/* Restore lazy mode */
- return xnthread_test_state(thread, XNROOT);
+ if (tsk_used_math(p) == 0)
+ return 0;
+ if (xnthread_test_state(thread, XNROOT))
+ return 1;
+
+ /*
+ * If we never switched fpu, and the cpu has fxsr, the
+ * last context switch saved fpu but did not
+ * reinitialize it, so we can simply reenable fpu
+ */
+ if (cpu_has_fxsr &&
+ (from == thread ||
+ (from && from->tcb.fpup == thread->tcb.fpup))) {
+ clts();
+ wrap_set_fpu_used(p);
+ return thread != from;
+ }
+ }
/*
* Restore the FPU hardware with valid fp registers from a
@@ -300,7 +318,7 @@ int xnarch_switch_fpu(struct xnthread *from, struct
xnthread *thread)
clts();
__do_restore_i387(x86_fpustate_ptr(&p->thread));
- if (tcb->root_kfpu) {
+ if (root_kfpu) {
x86_fpustate_ptr(&p->thread) = tcb->fpup;
wrap_clear_fpu_used(p);
if (tcb->root_used_math == 0)
@@ -337,9 +355,6 @@ void xnarch_init_shadow_tcb(struct xnthread *thread)
#endif
tcb->fpup = x86_fpustate_ptr(&p->thread);
tcb->root_kfpu = 0;
-
- if (xnthread_test_state(thread, XNUSER))
- xnthread_set_state(thread, XNFPU);
}
int xnarch_escalate(void)
--
1.7.10.4
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