vmm: make output for failed vmexits more threadsafe

If you had concurrent threads vmexit and the 2LS was unable to handle
the exits, you'd get an unintelligible mess.

This commit removes some unnecessary info - namely all of the info in
handle_vmexit() - and protects all of the output with a single lock.
It's not super elegant, and other printing can interfere with the
output, but it helps when there is a coordinated failure across numerous
threads.

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>

diff --git a/user/vmm/sched.c b/user/vmm/sched.c
index 280e39e..c91753b 100644 (file)
--- a/user/vmm/sched.c
+++ b/user/vmm/sched.c
@@ -421,10 +421,10 @@ static void __ctlr_entry(void)
 
        if (!handle_vmexit(cth->buddy)) {
                struct vm_trapframe *vm_tf = gth_to_vmtf(cth->buddy);
+               static struct spin_pdr_lock spew = SPINPDR_INITIALIZER;
 
-               fprintf(stderr, "vmm: handle_vmexit returned false\n");
-               fprintf(stderr,
-                       "Note: this may be a kernel module, not the kernel\n");
+               spin_pdr_lock(&spew);
+               fprintf(stderr, "vmm: handle_vmexit failed!\n");
                fprintf(stderr, "RSP was %p, ", (void *)vm_tf->tf_rsp);
                fprintf(stderr, "RIP was %p:\n", (void *)vm_tf->tf_rip);
                /* TODO: properly walk the kernel page tables to map the tf_rip
@@ -433,6 +433,7 @@ static void __ctlr_entry(void)
                 */
                hexdump(stderr, (void *)(vm_tf->tf_rip & 0x3fffffff), 16);
                showstatus(stderr, cth->buddy);
+               spin_pdr_unlock(&spew);
                exit(0);
        }
        /* We want to atomically yield and start/reenqueue our buddy.  We do so

diff --git a/user/vmm/vmexit.c b/user/vmm/vmexit.c
index 0cbff79..331633a 100644 (file)
--- a/user/vmm/vmexit.c
+++ b/user/vmm/vmexit.c
@@ -418,11 +418,6 @@ bool handle_vmexit(struct guest_thread *gth)
                /* TODO: just ignore these? */
                return TRUE;
        default:
-               fprintf(stderr,
-                       "VMM library: don't know how to handle exit %d\n",
-                       vm_tf->tf_exit_reason);
-               fprintf(stderr, "RIP %p, shutdown 0x%x\n", vm_tf->tf_rip,
-                       vm_tf->tf_exit_reason);
                return FALSE;
        }
 }