Date: Fri, 03 Oct 2014 17:25:33 +0900 (JST) From: Kohji Okuno <okuno.kohji@jp.panasonic.com> To: freebsd-current@freebsd.org Cc: okuno.kohji@jp.panasonic.com Subject: About pmap_mapdev() & pmap_unmapdev() Message-ID: <20141003.172533.863334695746935674.okuno.kohji@jp.panasonic.com>
next in thread | raw e-mail | index | archive | help
Hi,
At least in i386 && 9-stable, when we call pmap_mapdev() and
pmap_unmapdev(), kernel_pmap.pm_stats.resident_count is decreased
incorrectly.
pmap_mapdev_attr()->pmap_kenter_attr():
In this path, kernel_pmap.pm_stats.resident_count is not increlmented.
pmap_unmapdev()->kmem_free(kernel_map)->vm_map_remove()->pmap_remove():
But, in this path, kernel_pmap.pm_stats.resident_count is decreased in
pmap_remove_pte().
While I called pmap_mapdev() and pmap_unmapdev() repeatedly and
kernel_pmap.pm_stats.resident_count became `0', since pmap_remove()
returned without removing ptes, I encountered various kernel panics.
And, when I enabled INVARIANTS, I looked the following panic message.
panic: vm_page_free_toq: freeing mapped page 0xXXXXXXXX.
I think, I should change the following.
What do you think about this?
diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index 2adc6f8..a0998e8 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -5061,6 +5061,7 @@ pmap_mapdev_attr(vm_paddr_t pa, vm_size_t size, int mode)
{
vm_offset_t va, offset;
vm_size_t tmpsize;
+ int kmem_allocated = 0;
offset = pa & PAGE_MASK;
size = roundup(offset + size, PAGE_SIZE);
@@ -5068,13 +5069,18 @@ pmap_mapdev_attr(vm_paddr_t pa, vm_size_t size, int mode)
if (pa < KERNLOAD && pa + size <= KERNLOAD)
va = KERNBASE + pa;
- else
+ else {
va = kmem_alloc_nofault(kernel_map, size);
+ kmem_allocated = 1;
+ }
if (!va)
panic("pmap_mapdev: Couldn't alloc kernel virtual memory");
- for (tmpsize = 0; tmpsize < size; tmpsize += PAGE_SIZE)
+ for (tmpsize = 0; tmpsize < size; tmpsize += PAGE_SIZE) {
pmap_kenter_attr(va + tmpsize, pa + tmpsize, mode);
+ if (kmem_allocated)
+ kernel_pmap.pm_stats.resident_count++;
+ }
pmap_invalidate_range(kernel_pmap, va, va + tmpsize);
pmap_invalidate_cache_range(va, va + size);
return ((void *)(va + offset));
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20141003.172533.863334695746935674.okuno.kohji>