Fixes vmm_struct_cleanup

Cleanup is called from __proc_free, and I don't want to sleep in there.

Running the existing code with the lock debugger will flip out.  Even
attempting to qlock while holding a spinlock will panic, rightly so.
The lock held happens to be the parent's child lock, which it holds when
it decrefs the child.  Regardless, proc_decref is called all over the
place, and I'd rather not sleep in the release method.

I considered removing the qlock and having a multi-state atomic_t that
we CAS on, solving the issue of multiple potential initializers and
cleanup not checking the lock.  But that's a bit of overkill.

kern/arch/x86/vmm/vmm.c

diff --git a/kern/arch/x86/vmm/vmm.c b/kern/arch/x86/vmm/vmm.c
index 7a8f8d2..4af9853 100644
--- a/kern/arch/x86/vmm/vmm.c
+++ b/kern/arch/x86/vmm/vmm.c
@@ -80,6 +80,8 @@
 		qunlock(&vmm->qlock);
 		return 0;
 	}
+	/* Set this early, so cleanup checks the gpc array */
+	vmm->vmmcp = TRUE;
 	nr_guest_pcores = MIN(nr_guest_pcores, num_cpus);
 	vmm->amd = 0;
 	vmm->guest_pcores = kzmalloc(sizeof(void*) * nr_guest_pcores, KMALLOC_WAIT);
@@ -92,23 +94,21 @@
 		}
 	}
 	vmm->nr_guest_pcores = i;
-	vmm->vmmcp = TRUE;
 	qunlock(&vmm->qlock);
 	return i;
 }
 
-void vmm_struct_cleanup(struct vmm *vmm)
+/* Has no concurrency protection - only call this when you know you have the
+ * only ref to vmm.  For instance, from __proc_free, where there is only one ref
+ * to the proc (and thus proc.vmm). */
+void __vmm_struct_cleanup(struct vmm *vmm)
 {
-	qlock(&vmm->qlock);
-	if (!vmm->vmmcp) {
-		qunlock(&vmm->qlock);
+	if (!vmm->vmmcp)
 		return;
-	}
 	for (int i = 0; i < vmm->nr_guest_pcores; i++) {
 		if (vmm->guest_pcores[i])
 			vmx_destroy_vcpu(vmm->guest_pcores[i]);
 	}
 	kfree(vmm->guest_pcores);
 	vmm->vmmcp = FALSE;
-	qunlock(&vmm->qlock);
 }

kern/arch/x86/vmm/vmm.h

diff --git a/kern/arch/x86/vmm/vmm.h b/kern/arch/x86/vmm/vmm.h
index 27f248b..5945df5 100644
--- a/kern/arch/x86/vmm/vmm.h
+++ b/kern/arch/x86/vmm/vmm.h
@@ -41,7 +41,7 @@
 void vmm_pcpu_init(void);
 
 int vmm_struct_init(struct vmm *vmm, unsigned int nr_guest_pcores);
-void vmm_struct_cleanup(struct vmm *vmm);
+void __vmm_struct_cleanup(struct vmm *vmm);
 
 int vm_run(uint64_t,uint64_t, uint64_t);
 int intel_vmx_start(int id);

kern/src/process.c

diff --git a/kern/src/process.c b/kern/src/process.c
index 68b3357..3b05c08 100644
--- a/kern/src/process.c
+++ b/kern/src/process.c
@@ -458,7 +458,7 @@
 	assert(kref_refcnt(&p->p_kref) == 0);
 	assert(TAILQ_EMPTY(&p->alarmset.list));
 
-	vmm_struct_cleanup(&p->vmm);
+	__vmm_struct_cleanup(&p->vmm);
 	p->progname[0] = 0;
 	cclose(p->dot);
 	cclose(p->slash);