[src/trunk]: src/sys/arch/amd64/amd64 On amd64, Xen PV calls syscalls and tra...

[bouyer <bouyer%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/91ac16c0ef60
branches:  trunk
changeset: 934981:91ac16c0ef60
user:      bouyer <bouyer%NetBSD.org@localhost>
date:      Sun Jun 21 16:57:18 2020 +0000

description:
On amd64, Xen PV calls syscalls and traps with events enabled.
Disable events on entry to be safe.
It should have been mostly safe for most cases, but for FPU traps
we need to reload the FPU state if we got interrupted at trap entry.

Hopefully fixes:
panic: kernel diagnostic assertion "curlwp->l_md.md_flags & MDL_FPU_IN_CPU" failed: file "/home/source/ab/HEAD/src/sys/arch/x86/x86/fpu.c", line 524

when running tests.

diffstat:

 sys/arch/amd64/amd64/amd64_trap.S |  26 +++++++++++++++++---------
 sys/arch/amd64/amd64/locore.S     |  13 +++++++++++--
 2 files changed, 28 insertions(+), 11 deletions(-)

diffs (124 lines):

diff -r a0a0a87fc3e1 -r 91ac16c0ef60 sys/arch/amd64/amd64/amd64_trap.S
--- a/sys/arch/amd64/amd64/amd64_trap.S Sun Jun 21 16:53:57 2020 +0000
+++ b/sys/arch/amd64/amd64/amd64_trap.S Sun Jun 21 16:57:18 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: amd64_trap.S,v 1.51 2019/12/07 10:19:35 maxv Exp $     */
+/*     $NetBSD: amd64_trap.S,v 1.52 2020/06/21 16:57:18 bouyer Exp $   */
 
 /*
  * Copyright (c) 1998, 2007, 2008, 2017 The NetBSD Foundation, Inc.
@@ -90,7 +90,7 @@
  */
 
 #ifdef XENPV
-#define        PRE_TRAP        movq (%rsp),%rcx ; movq 8(%rsp),%r11 ; addq $0x10,%rsp
+#define        PRE_TRAP        CLI(cx); movq (%rsp),%rcx ; movq 8(%rsp),%r11 ; addq $0x10,%rsp
 #else
 #define        PRE_TRAP
 #endif
@@ -231,9 +231,9 @@
        movw    %ds,TF_DS(%rsp)
 
        jmp     .Lalltraps_noentry
-#else
+#else /* !XENPV */
        ZTRAP(T_TRCTRAP)
-#endif
+#endif /* !XENPV */
 IDTVEC_END(trap01)
 
 /*
@@ -250,7 +250,7 @@
 IDTVEC(trap02)
 #if defined(XENPV)
        ZTRAP(T_NMI)
-#else
+#else /* XENPV */
        ZTRAP_NJ(T_NMI)
        subq    $TF_REGSIZE,%rsp
        INTR_SAVE_GPRS
@@ -299,7 +299,7 @@
        INTR_RESTORE_GPRS
        addq    $TF_REGSIZE+16,%rsp
        iretq
-#endif
+#endif /* XENPV */
 IDTVEC_END(trap02)
 
 IDTVEC(trap03)
@@ -361,7 +361,7 @@
 IDTVEC(trap08)
 #if defined(XENPV)
        TRAP(T_DOUBLEFLT)
-#else
+#else /* XENPV */
        TRAP_NJ(T_DOUBLEFLT)
        subq    $TF_REGSIZE,%rsp
        INTR_SAVE_GPRS
@@ -396,7 +396,7 @@
        INTR_RESTORE_GPRS
        addq    $TF_REGSIZE+16,%rsp
        iretq
-#endif
+#endif /* XENPV */
 IDTVEC_END(trap08)
 
 IDTVEC(trap09)
@@ -414,7 +414,7 @@
  * in order to copy the user segment registers into the fault frame.
  */
 #define kernuser_reenter alltraps
-#endif
+#endif /* XENPV */
 
 IDTVEC(trap11)         /* #NP() Segment not present */
        TRAP_NJ(T_SEGNPFLT)
@@ -448,6 +448,14 @@
        ZTRAP_NJ(T_ARITHTRAP)
 .Ldo_fputrap:
        INTRENTRY
+#ifdef XENPV
+       /* traps are called with interrupts enabled, and we may have been
+        * interrupted just before the CLI in the trap macro.
+        * we have to check if a FPU reload is needed.
+        */ 
+       movq    CPUVAR(CURLWP),%r14
+       HANDLE_DEFERRED_FPU
+#endif /* XENPV */
 #ifdef DIAGNOSTIC
        movl    CPUVAR(ILEVEL),%ebx
 #endif
diff -r a0a0a87fc3e1 -r 91ac16c0ef60 sys/arch/amd64/amd64/locore.S
--- a/sys/arch/amd64/amd64/locore.S     Sun Jun 21 16:53:57 2020 +0000
+++ b/sys/arch/amd64/amd64/locore.S     Sun Jun 21 16:57:18 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore.S,v 1.209 2020/05/27 19:33:40 ad Exp $  */
+/*     $NetBSD: locore.S,v 1.210 2020/06/21 16:57:18 bouyer Exp $      */
 
 /*
  * Copyright-o-rama!
@@ -1481,7 +1481,13 @@
        movq    $2,TF_ERR(%rsp)         /* syscall instruction size */
        movq    $T_ASTFLT,TF_TRAPNO(%rsp)
 #else
-       /* Xen already switched to kernel stack */
+       /*
+        * Xen already switched to kernel stack.
+        * But it didn't disable events
+        */
+       pushq   %rsi
+       CLI(si)
+       popq    %rsi
        addq    $0x10,%rsp      /* gap to match cs:rip */
        pushq   $2              /* error code */
        pushq   $T_ASTFLT
@@ -1524,6 +1530,9 @@
        TEXT_USER_BEGIN
 IDTVEC(osyscall)
 #ifdef XENPV
+       pushq   %rsi
+       CLI(si)
+       popq    %rsi
        movq (%rsp),%rcx
        movq 8(%rsp),%r11
        addq $0x10,%rsp