Commit 65e074df authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar

x86: cpa, preserve large pages if possible

When CPA is called on a range which fits into a large page mapping,
avoid to split the page when:

1) There is no change of attributes
2) The range to change is a complete large mapping
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f4ae5da0
......@@ -18,12 +18,17 @@
struct cpa_data {
unsigned long vaddr;
int numpages;
pgprot_t mask_set;
pgprot_t mask_clr;
int numpages;
int flushtlb;
};
enum {
CPA_NO_SPLIT = 0,
CPA_SPLIT,
};
static inline int
within(unsigned long addr, unsigned long start, unsigned long end)
{
......@@ -230,6 +235,86 @@ static void __set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
#endif
}
static int try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
{
unsigned long nextpage_addr, numpages, pmask, psize, flags;
pte_t new_pte, old_pte, *tmp;
pgprot_t old_prot, new_prot;
int level, res = CPA_SPLIT;
spin_lock_irqsave(&pgd_lock, flags);
/*
* Check for races, another CPU might have split this page
* up already:
*/
tmp = lookup_address(address, &level);
if (tmp != kpte)
goto out_unlock;
switch (level) {
case PG_LEVEL_2M:
psize = LARGE_PAGE_SIZE;
pmask = LARGE_PAGE_MASK;
break;
case PG_LEVEL_1G:
default:
res = -EINVAL;
goto out_unlock;
}
/*
* Calculate the number of pages, which fit into this large
* page starting at address:
*/
nextpage_addr = (address + psize) & pmask;
numpages = (nextpage_addr - address) >> PAGE_SHIFT;
if (numpages < cpa->numpages)
cpa->numpages = numpages;
/*
* We are safe now. Check whether the new pgprot is the same:
*/
old_pte = *kpte;
old_prot = new_prot = pte_pgprot(old_pte);
pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
new_prot = static_protections(new_prot, address);
/*
* If there are no changes, return. maxpages has been updated
* above:
*/
if (pgprot_val(new_prot) == pgprot_val(old_prot)) {
res = CPA_NO_SPLIT;
goto out_unlock;
}
/*
* We need to change the attributes. Check, whether we can
* change the large page in one go. We request a split, when
* the address is not aligned and the number of pages is
* smaller than the number of pages in the large page. Note
* that we limited the number of possible pages already to
* the number of pages in the large page.
*/
if (address == (nextpage_addr - psize) && cpa->numpages == numpages) {
/*
* The address is aligned and the number of pages
* covers the full page.
*/
new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));
__set_pmd_pte(kpte, address, new_pte);
cpa->flushtlb = 1;
res = CPA_NO_SPLIT;
}
out_unlock:
spin_unlock_irqrestore(&pgd_lock, flags);
return res;
}
static int split_large_page(pte_t *kpte, unsigned long address)
{
pgprot_t ref_prot = pte_pgprot(pte_clrhuge(*kpte));
......@@ -295,7 +380,7 @@ static int split_large_page(pte_t *kpte, unsigned long address)
static int __change_page_attr(unsigned long address, struct cpa_data *cpa)
{
struct page *kpte_page;
int level, err = 0;
int level, res;
pte_t *kpte;
repeat:
......@@ -338,13 +423,34 @@ static int __change_page_attr(unsigned long address, struct cpa_data *cpa)
set_pte_atomic(kpte, new_pte);
cpa->flushtlb = 1;
}
} else {
err = split_large_page(kpte, address);
if (!err)
goto repeat;
cpa->flushtlb = 1;
cpa->numpages = 1;
return 0;
}
return err;
/*
* Check, whether we can keep the large page intact
* and just change the pte:
*/
res = try_preserve_large_page(kpte, address, cpa);
if (res < 0)
return res;
/*
* When the range fits into the existing large page,
* return. cp->numpages and cpa->tlbflush have been updated in
* try_large_page:
*/
if (res == CPA_NO_SPLIT)
return 0;
/*
* We have to split the large page:
*/
res = split_large_page(kpte, address);
if (res)
return res;
cpa->flushtlb = 1;
goto repeat;
}
/**
......@@ -410,15 +516,27 @@ static int change_page_attr_addr(struct cpa_data *cpa)
static int __change_page_attr_set_clr(struct cpa_data *cpa)
{
unsigned int i;
int ret;
int ret, numpages = cpa->numpages;
for (i = 0; i < cpa->numpages ; i++, cpa->vaddr += PAGE_SIZE) {
while (numpages) {
/*
* Store the remaining nr of pages for the large page
* preservation check.
*/
cpa->numpages = numpages;
ret = change_page_attr_addr(cpa);
if (ret)
return ret;
}
/*
* Adjust the number of pages with the result of the
* CPA operation. Either a large page has been
* preserved or a single page update happened.
*/
BUG_ON(cpa->numpages > numpages);
numpages -= cpa->numpages;
cpa->vaddr += cpa->numpages * PAGE_SIZE;
}
return 0;
}
......
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