From: Tetsu Yamamoto <tyamamot@redhat.com>
Date: Tue, 5 Feb 2008 18:04:14 -0500
Subject: [Xen] ia64: stop all CPUs on HV panic part3
Message-id: 47A8EB6E.2080507@redhat.com
O-Subject: Re: [RHEL5.2 PATCH] [Xen] Dom0/DomU may continue to work after hypervisor panic
Bugzilla: 426129

Attached is an additional patch for BZ#426129.

https://bugzilla.redhat.com/show_bug.cgi?id=426129

The patch previously posted and committed in kernel -75 was not enough
to fix this problem, because it is still possible to enter the infinite
loop in debugger trap before all cpus are stopped.

This problem has been fixed in the upstream:
- [IA64] Fix infinite loop in fault handler if debugger is not connected
http://xenbits.xensource.com/ext/ia64/xen-unstable.hg?rev/33d0cf9474f9

However, to backport it to RHEL5, more patches to modify vmx_faults are
required, and it would be large.

Instead of that, the attached patch is minimized to avoid the debugger
trap, though it is different from the fix in the upstream.

I've tested this with kernel -77 and confirmed that Dom0 is stopped on
hypervisor panic.

Please review and ACK.

Regards,

Tetsu Yamamoto

Tetsu Yamamoto wrote::
> This patch fixes BZ#426129.
> https://bugzilla.redhat.com/show_bug.cgi?id=426129
>
> This is backported from the upstream to stop all CPUs on hypervisor panic.
> http://xenbits.xensource.com/ext/xen-ia64-unstable.hg?rev/124f7a7f5f84
>
> I've tested these patches with kernel-2.6.18-58.el5, and confirmed that
> Dom0 is stopped on hypervisor panic.
>
> Please review and ACK.
>
> Regards,
>
> Tetsu Yamamoto
>
>
>

diff --git a/common/gdbstub.c b/common/gdbstub.c
index 51a2d6c..70528e1 100644
--- a/common/gdbstub.c
+++ b/common/gdbstub.c
@@ -478,13 +478,13 @@ process_command(struct cpu_user_regs *regs, struct gdb_context *ctx)
     return resume;
 }
 
-static struct gdb_context
+struct gdb_context
 __gdb_ctx = {
     .serhnd  = -1,
     .running = ATOMIC_INIT(1),
     .signum  = 1
 };
-static struct gdb_context *gdb_ctx = &__gdb_ctx;
+struct gdb_context *gdb_ctx = &__gdb_ctx;
 
 static void
 gdbstub_console_puts(const char *str)
diff --git a/include/asm-ia64/debugger.h b/include/asm-ia64/debugger.h
index 747e5a7..4e5652f 100644
--- a/include/asm-ia64/debugger.h
+++ b/include/asm-ia64/debugger.h
@@ -66,7 +66,11 @@ static inline int debugger_trap_fatal(
 
 #define ____debugger_trap_immediate(b) __asm__ __volatile__ ("break.m "#b"\n")
 #define __debugger_trap_immediate(b) ____debugger_trap_immediate(b)
-#define debugger_trap_immediate() __debugger_trap_immediate(CDB_BREAK_NUM)
+#define debugger_trap_immediate()					\
+do {									\
+    if ( gdb_ctx->serhnd >= 0 )						\
+        __debugger_trap_immediate(CDB_BREAK_NUM);			\
+} while (0)
 
 //XXX temporal work around
 #ifndef CONFIG_SMP
diff --git a/include/xen/gdbstub.h b/include/xen/gdbstub.h
index 46e4815..2009a42 100644
--- a/include/xen/gdbstub.h
+++ b/include/xen/gdbstub.h
@@ -47,6 +47,7 @@ struct gdb_context {
     unsigned long       out_offset;
     u8                  out_csum;
 };
+extern struct gdb_context *gdb_ctx;
 
 /* interface to arch specific routines */
 void gdb_write_to_packet(