svn commit: r283014 - head/sys/arm/arm
Warner Losh
imp at FreeBSD.org
Sat May 16 21:24:33 UTC 2015
Author: imp
Date: Sat May 16 21:24:32 2015
New Revision: 283014
URL: https://svnweb.freebsd.org/changeset/base/283014
Log:
Don't allow unmapped I/O. The pmap isn't quite up to the task. Add a
comment to this effect and switch the default. My old AT91SAM9G20
now boots, fsck's the SD card and runs w/o an issue for the first
time since a 9.1-ish stable build I did a few years ago.
Problems with unmapped I/O:
o un-page-aligned I/O requests to devices fail (notably fsck
and newfs).
o write-back caching was totally broken. write-through caching
needed to be enabled.
o Even page-aligned I/O requests sometimes failed for reasons
not thoroughly investigated.
Suggested by: ian@
MFC after: 2 days
Modified:
head/sys/arm/arm/pmap.c
Modified: head/sys/arm/arm/pmap.c
==============================================================================
--- head/sys/arm/arm/pmap.c Sat May 16 21:08:33 2015 (r283013)
+++ head/sys/arm/arm/pmap.c Sat May 16 21:24:32 2015 (r283014)
@@ -4310,7 +4310,13 @@ pmap_copy_page(vm_page_t src, vm_page_t
pmap_copy_page_func(VM_PAGE_TO_PHYS(src), VM_PAGE_TO_PHYS(dst));
}
-int unmapped_buf_allowed = 1;
+/*
+ * We have code to do unmapped I/O. However, it isn't quite right
+ * an causes un-page-aligned I/O to devices to fail (most notably
+ * newfs or fsck). We give up a little performance to do this, but
+ * we trade that for rock-solid stability so it is a good trade.
+ */
+int unmapped_buf_allowed = 0;
void
pmap_copy_pages(vm_page_t ma[], vm_offset_t a_offset, vm_page_t mb[],
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