git: 818390ce0ca5 - main - arm64: fix early devmap assertion

[Mitchell Horne]

The branch main has been updated by mhorne:

URL: https://cgit.FreeBSD.org/src/commit/?id=818390ce0ca539300dd15d7a817784f1e3f7a9b8

commit 818390ce0ca539300dd15d7a817784f1e3f7a9b8
Author:     Mitchell Horne <mhorne at FreeBSD.org>
AuthorDate: 2021-01-13 18:30:50 +0000
Commit:     Mitchell Horne <mhorne at FreeBSD.org>
CommitDate: 2021-01-13 21:27:44 +0000

    arm64: fix early devmap assertion
    
    The purpose of this KASSERT is to ensure that we do not run out of space
    in the early devmap. However, the devmap grew beyond its initial size of
    2MB in r336519, and this assertion did not grow with it.
    
    A devmap mapping of a 1080p framebuffer requires 1920x1080 bytes, or
    1.977 MB, so it is just barely able to fit without triggering the
    assertion, provided no other devices are mapped before it. With the
    addition of `options GDB` in GENERIC by bbfa199cbc16, the uart is now
    mapped for the purposes of a debug port, before mapping the framebuffer.
    The presence of both these conditions pushes the selected virtual
    address just below the threshold, triggering the assertion.
    
    To fix this, use the correct size of the devmap, defined by
    PMAP_MAPDEV_EARLY_SIZE. Since this code is shared with RISC-V, define
    it for that platform as well (although it is a different size).
    
    PR:             25241
    Reported by:    gbe
    MFC after:      3 days
    Sponsored by:   The FreeBSD Foundation
---
 sys/kern/subr_devmap.c      | 2 +-
 sys/riscv/include/vmparam.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/sys/kern/subr_devmap.c b/sys/kern/subr_devmap.c
index 581e85086f0f..8e07199b7f73 100644
--- a/sys/kern/subr_devmap.c
+++ b/sys/kern/subr_devmap.c
@@ -275,7 +275,7 @@ pmap_mapdev(vm_offset_t pa, vm_size_t size)
 	if (early_boot) {
 		akva_devmap_vaddr = trunc_page(akva_devmap_vaddr - size);
 		va = akva_devmap_vaddr;
-		KASSERT(va >= VM_MAX_KERNEL_ADDRESS - L2_SIZE,
+		KASSERT(va >= VM_MAX_KERNEL_ADDRESS - PMAP_MAPDEV_EARLY_SIZE,
 		    ("Too many early devmap mappings"));
 	} else
 #endif
diff --git a/sys/riscv/include/vmparam.h b/sys/riscv/include/vmparam.h
index f3cab1074454..9580ab3e1218 100644
--- a/sys/riscv/include/vmparam.h
+++ b/sys/riscv/include/vmparam.h
@@ -235,6 +235,7 @@ extern vm_offset_t init_pt_va;
 #define	ZERO_REGION_SIZE	(64 * 1024)	/* 64KB */
 
 #define	DEVMAP_MAX_VADDR	VM_MAX_KERNEL_ADDRESS
+#define	PMAP_MAPDEV_EARLY_SIZE	(L2_SIZE * 2)
 
 /*
  * No non-transparent large page support in the pmap.