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Enhance pmap_change_attr(). Use pmap_demote_pde() to demote a 2MB page

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mapping to 4KB page mappings when the specified attribute change only
applies to a portion of the 2MB page.  Previously, in such cases,
pmap_change_attr() gave up and returned an error.

Submitted by:	Magesh Dhasayyan
This commit is contained in:
Alan Cox 2008-07-27 17:32:36 +00:00
parent 5573021d78
commit 91842e53a9
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=180845
1 changed files with 22 additions and 9 deletions
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31
sys/amd64/amd64/pmap.c
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@ -4373,27 +4373,40 @@ pmap_change_attr(va, size, mode)
return (EINVAL);
/*
* XXX: We have to support tearing 2MB pages down into 4k pages if
* needed here.
* Pages that aren't mapped aren't supported. Also break down 2MB pages
* into 4KB pages if required.
*/
/* Pages that aren't mapped aren't supported. */
for (tmpva = base; tmpva < (base + size); ) {
PMAP_LOCK(kernel_pmap);
for (tmpva = base; tmpva < base + size; ) {
pde = pmap_pde(kernel_pmap, tmpva);
if (*pde == 0)
if (*pde == 0) {
PMAP_UNLOCK(kernel_pmap);
return (EINVAL);
}
if (*pde & PG_PS) {
/* Handle 2MB pages that are completely contained. */
if (size >= NBPDR) {
/*
* If the current offset aligns with a 2MB page frame
* and there is at least 2MB left within the range, then
* we need not break down this page into 4KB pages.
*/
if ((tmpva & PDRMASK) == 0 &&
tmpva + PDRMASK < base + size) {
tmpva += NBPDR;
continue;
}
return (EINVAL);
if (!pmap_demote_pde(kernel_pmap, pde, tmpva)) {
PMAP_UNLOCK(kernel_pmap);
return (ENOMEM);
}
}
pte = vtopte(tmpva);
if (*pte == 0)
if (*pte == 0) {
PMAP_UNLOCK(kernel_pmap);
return (EINVAL);
}
tmpva += PAGE_SIZE;
}
PMAP_UNLOCK(kernel_pmap);
/*
* Ok, all the pages exist, so run through them updating their