When doing AST processing:

1) block interrupts, then check for ASTs
2) if no ASTs, return with interrupts blocked, so they can be re-enabled
   ATOMICALLY in the return to userspace
3) if an AST happened, then re-enable interrupts, call ast(), then goto 1

ok jsg@

diff --git a/sys/arch/riscv64/riscv64/exception.S b/sys/arch/riscv64/riscv64/exception.S
index 316447f..719f9ab 100644 (file)
--- a/sys/arch/riscv64/riscv64/exception.S
+++ b/sys/arch/riscv64/riscv64/exception.S
@@ -1,4 +1,4 @@
-/*     $OpenBSD: exception.S,v 1.3 2021/05/10 05:58:20 jsg Exp $       */
+/*     $OpenBSD: exception.S,v 1.4 2021/05/13 06:44:11 kettenis Exp $  */
 
 /*-
  * Copyright (c) 2015-2018 Ruslan Bukin <br@bsdpad.com>
@@ -183,9 +183,8 @@
 .endm
 
 .macro do_ast
-       /* Disable interrupts */
-       csrr    a4, sstatus
 1:
+       /* Disable interrupts */
        csrci   sstatus, (SSTATUS_SIE)
 
        /* Check for astpending */
@@ -196,8 +195,8 @@
 
        sw      x0, P_ASTPENDING(a1)
 
-       /* Restore interrupts */
-       csrw    sstatus, a4
+       /* Enable interrupts */
+       csrsi   sstatus, (SSTATUS_SIE)
 
        /* handle the ast */
        mv      a0, sp