gdbstub: manage CPUs as threads (Jan Kiszka)

This patch enhances QEMU's built-in debugger for SMP guest debugging.
Using the thread support of the gdb remote protocol, each VCPU is mapped
on a pseudo thread and exposed to the gdb frontend. This way you can
easy switch the focus of gdb between the VCPUs and observe their states.
On breakpoint hit, the focus is automatically adjusted just as for
normal multi-threaded application under gdb control.

Furthermore, the patch propagates breakpoint and watchpoint insertions
or removals to all CPUs, not just the current one as it was the case so
far. Without this, SMP guest debugging was practically unfeasible.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5743 c046a42c-6fe2-441c-8c8c-71466251a162

gdbstub.h

@@ -8,6 +8,7 @@ typedef void (*gdb_syscall_complete_cb)(CPUState *env,
 
 void gdb_do_syscall(gdb_syscall_complete_cb cb, const char *fmt, ...);
 int use_gdb_syscalls(void);
+void gdb_set_stop_cpu(CPUState *env);
 #ifdef CONFIG_USER_ONLY
 int gdb_handlesig (CPUState *, int);
 void gdb_exit(CPUState *, int);

vl.c

@@ -3720,6 +3720,7 @@ static int main_loop(void)
                 ret = EXCP_INTERRUPT;
             }
             if (unlikely(ret == EXCP_DEBUG)) {
+                gdb_set_stop_cpu(cur_cpu);
                 vm_stop(EXCP_DEBUG);
             }
             /* If all cpus are halted then wait until the next IRQ */