From 133898afd5440e97ebba4136468813656a7679af Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Mon, 6 Jul 2009 18:43:42 +0000 Subject: 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) --- sys/amd64/amd64/pmap.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'sys/amd64') diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c index eb09d4125c87..5bf8b890e103 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)); -- cgit v1.2.3