[src-draft/trunk]: src/sys/arch/arm/vfp Add kthread_fpu_enter/exit support to...

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src-all/rev/88114cdf465e
branches:  trunk
changeset: 936594:88114cdf465e
user:      Taylor R Campbell <riastradh%NetBSD.org@localhost>
date:      Fri Jul 31 03:11:19 2020 +0000

description:
Add kthread_fpu_enter/exit support to arm.

diffstat:

 sys/arch/arm/vfp/vfp_init.c |  44 ++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 42 insertions(+), 2 deletions(-)

diffs (91 lines):

diff -r 3a9b1ca3581a -r 88114cdf465e sys/arch/arm/vfp/vfp_init.c
--- a/sys/arch/arm/vfp/vfp_init.c       Fri Jul 31 03:10:13 2020 +0000
+++ b/sys/arch/arm/vfp/vfp_init.c       Fri Jul 31 03:11:19 2020 +0000
@@ -38,6 +38,7 @@
 #include <sys/types.h>
 #include <sys/systm.h>
 #include <sys/device.h>
+#include <sys/kthread.h>
 #include <sys/proc.h>
 #include <sys/cpu.h>
 
@@ -504,7 +505,8 @@
                return 1;
 
        /* This shouldn't ever happen.  */
-       if (fault_code != FAULT_USER)
+       if (fault_code != FAULT_USER &&
+           (curlwp->l_flag & (LW_SYSTEM|LW_SYSTEM_FPU)) == LW_SYSTEM)
                panic("NEON fault in non-user mode");
 
        /* if we already own the FPU and it's enabled, raise SIGILL */
@@ -668,6 +670,19 @@
            sizeof(mcp->__fpu.__vfpregs.__vfp_fstmx));
 }
 
+/*
+ * True if this is a system thread with its own private FPU state.
+ */
+static inline bool
+lwp_system_fpu_p(struct lwp *l)
+{
+
+       return (l->l_flag & (LW_SYSTEM|LW_SYSTEM_FPU)) ==
+           (LW_SYSTEM|LW_SYSTEM_FPU);
+}
+
+static const struct vfpreg zero_vfpreg;
+
 void
 fpu_kern_enter(void)
 {
@@ -675,6 +690,11 @@
        uint32_t fpexc;
        int s;
 
+       if (lwp_system_fpu_p(curlwp) && !cpu_intr_p()) {
+               KASSERT(!cpu_softintr_p());
+               return;
+       }
+
        /*
         * Block interrupts up to IPL_VM.  We must block preemption
         * since -- if this is a user thread -- there is nowhere to
@@ -701,11 +721,15 @@
 void
 fpu_kern_leave(void)
 {
-       static const struct vfpreg zero_vfpreg;
        struct cpu_info *ci = curcpu();
        int s;
        uint32_t fpexc;
 
+       if (lwp_system_fpu_p(curlwp) && !cpu_intr_p()) {
+               KASSERT(!cpu_softintr_p());
+               return;
+       }
+
        KASSERT(ci->ci_cpl == IPL_VM);
        KASSERT(ci->ci_kfpu_spl != -1);
 
@@ -730,4 +754,20 @@
        splx(s);
 }
 
+void
+kthread_fpu_enter_md(void)
+{
+
+       pcu_load(&arm_vfp_ops);
+}
+
+void
+kthread_fpu_exit_md(void)
+{
+
+       /* XXX Should vfp_state_release zero the registers itself?  */
+       load_vfpregs(&zero_vfpreg);
+       vfp_discardcontext(curlwp, 0);
+}
+
 #endif /* FPU_VFP */