panic booting with if_tap_load="YES" in loader.conf

[Konstantin Belousov]

On Sat, May 18, 2019 at 01:33:28AM -0400, Mark Johnston wrote:
> On Fri, May 17, 2019 at 10:18:57PM -0600, Rebecca Cran wrote:
> > I just updated from r346856 to r347950 and ran into a new panic, caused
> > by having if_tap_load="YES" in /boot/loader.conf - because it's already
> > built-in to the kernel:
> 
> I think this patch should fix the panic, but I only compile-tested it.
> I considered having the logic live in preload_delete_name() instead, but
> the boot-time ucode code must still defer the deletion somewhat.

Try this instead.  I will revert r347931 after this landed, or could keep
it alone.

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 1cf09dc5cb7..03fe8a5d096 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1616,6 +1616,13 @@ hammer_time(u_int64_t modulep, u_int64_t physfree)
 	bzero((void *)thread0.td_kstack, kstack0_sz);
 	physfree += kstack0_sz;
 
+	/*
+	 * Initialize enough of thread0 for delayed invalidation to
+	 * work very early.  Rely on thread0.td_base_pri
+	 * zero-initialization, it is reset to PVM at proc0_init().
+	 */
+	pmap_thread_init_invl_gen(&thread0);
+
 	/*
 	 * make gdt memory segments
 	 */
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 7997a9f65dc..ecd701399fc 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -700,9 +700,12 @@ pmap_delayed_invl_start_u(void)
 	invl_gen = &td->td_md.md_invl_gen;
 	PMAP_ASSERT_NOT_IN_DI();
 	lock_delay_arg_init(&lda, &di_delay);
+	pri = td->td_base_pri;
+	if (pri <= PVM)
+		goto again;
 	thread_lock(td);
 	pri = td->td_base_pri;
-	if (pri < PVM) {
+	if (pri <= PVM) {
 		invl_gen->saved_pri = 0;
 	} else {
 		invl_gen->saved_pri = pri;