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author | alc <alc@FreeBSD.org> | 2009-07-06 18:43:42 +0000 |
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committer | alc <alc@FreeBSD.org> | 2009-07-06 18:43:42 +0000 |
commit | c9ef1e01042ca2bf24cdc667b8706fa633692304 (patch) | |
tree | 7999744132a8c42bf992b2aa7b595626d4583faf /sys/amd64 | |
parent | 19e5186727eceb4c07892bc93ebd663e5b022341 (diff) | |
download | FreeBSD-src-c9ef1e01042ca2bf24cdc667b8706fa633692304.zip FreeBSD-src-c9ef1e01042ca2bf24cdc667b8706fa633692304.tar.gz |
When pmap_change_attr() changes the PAT setting on a kernel mapping, it has
to simultaneously change the PAT setting for the same pages within the
direct map region. This may require the demotion of a 2MB page mapping and
the allocation of a page table page. This revision gives the highest
possible priority (VM_ALLOC_INTERRUPT) to this page allocation, so that
pmap_change_attr() is less likely to fail. (In general, kernel page table
page allocations have the highest priority, so this is not creating a new
precedent.)
(Demotion of 1GB page mappings within the direct map already specifies
VM_ALLOC_INTERRUPT to vm_page_alloc(), so only pmap_demote_pde() must be
changed.)
Approved by: re (kib)
Diffstat (limited to 'sys/amd64')
-rw-r--r-- | sys/amd64/amd64/pmap.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c index eb09d41..5bf8b89 100644 --- a/sys/amd64/amd64/pmap.c +++ b/sys/amd64/amd64/pmap.c @@ -2218,11 +2218,19 @@ pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va) /* * Invalidate the 2MB page mapping and return "failure" if the * mapping was never accessed or the allocation of the new - * page table page fails. + * page table page fails. If the 2MB page mapping belongs to + * the direct map region of the kernel's address space, then + * the page allocation request specifies the highest possible + * priority (VM_ALLOC_INTERRUPT). Otherwise, the priority is + * normal. Page table pages are preallocated for every other + * part of the kernel address space, so the direct map region + * is the only part of the kernel address space that must be + * handled here. */ if ((oldpde & PG_A) == 0 || (mpte = vm_page_alloc(NULL, - pmap_pde_pindex(va), VM_ALLOC_NOOBJ | VM_ALLOC_NORMAL | - VM_ALLOC_WIRED)) == NULL) { + pmap_pde_pindex(va), (va >= DMAP_MIN_ADDRESS && va < + DMAP_MAX_ADDRESS ? VM_ALLOC_INTERRUPT : VM_ALLOC_NORMAL) | + VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) { free = NULL; pmap_remove_pde(pmap, pde, trunc_2mpage(va), &free); pmap_invalidate_page(pmap, trunc_2mpage(va)); |