amd64: rework AP startup

Stop using temporal page table with 1:1 mapping of low 1G populated over
the whole VA.  Use 1:1 mapping of low 4G temporarily installed in the
normal kernel page table.

The features are:
- now there is one less step for startup asm to perform
- the startup code still needs to be at lower 1G because CPU starts in
  real mode. But everything else can be located anywhere in low 4G
  because it is accessed by non-paged 32bit protected mode.  Note that
  kernel page table root page is at low 4G, as well as the kernel itself.
- the page table pages can be allocated by normal allocator, there is
  no need to carve them from the phys_avail segments at very early time.
  The allocation of the page for startup code still requires some magic.
  Pages are freed after APs are ignited.
- la57 startup for APs is less tricky, we directly load the final page
  table and do not need to tweak the paging mode.

Reviewed by:	markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D31121

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 1bd2c8c0afe0..49e245e1fdfe 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1279,7 +1279,7 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 	 * in real mode mode (e.g. SMP bare metal).
 	 */
 #ifdef SMP
-	mp_bootaddress(physmap, &physmap_idx);
+	alloc_ap_trampoline(physmap, &physmap_idx);
 #endif
 
 	/* call pmap initialization to make new kernel address space */