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: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Thomas Gleixner
Ingo Molnar
parent
f4ae5da0e8
commit
65e074dffa
@ -18,12 +18,17 @@
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struct cpa_data {
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unsigned long vaddr;
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int numpages;
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pgprot_t mask_set;
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pgprot_t mask_clr;
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int numpages;
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int flushtlb;
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};
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enum {
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CPA_NO_SPLIT = 0,
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CPA_SPLIT,
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};
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static inline int
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within(unsigned long addr, unsigned long start, unsigned long end)
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{
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@ -230,6 +235,86 @@ static void __set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
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#endif
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}
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static int try_preserve_large_page(pte_t *kpte, unsigned long address,
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struct cpa_data *cpa)
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{
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unsigned long nextpage_addr, numpages, pmask, psize, flags;
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pte_t new_pte, old_pte, *tmp;
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pgprot_t old_prot, new_prot;
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int level, res = CPA_SPLIT;
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spin_lock_irqsave(&pgd_lock, flags);
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/*
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* Check for races, another CPU might have split this page
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* up already:
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*/
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tmp = lookup_address(address, &level);
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if (tmp != kpte)
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goto out_unlock;
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switch (level) {
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case PG_LEVEL_2M:
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psize = LARGE_PAGE_SIZE;
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pmask = LARGE_PAGE_MASK;
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break;
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case PG_LEVEL_1G:
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default:
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res = -EINVAL;
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goto out_unlock;
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}
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/*
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* Calculate the number of pages, which fit into this large
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* page starting at address:
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*/
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nextpage_addr = (address + psize) & pmask;
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numpages = (nextpage_addr - address) >> PAGE_SHIFT;
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if (numpages < cpa->numpages)
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cpa->numpages = numpages;
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/*
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* We are safe now. Check whether the new pgprot is the same:
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*/
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old_pte = *kpte;
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old_prot = new_prot = pte_pgprot(old_pte);
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pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
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pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
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new_prot = static_protections(new_prot, address);
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/*
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* If there are no changes, return. maxpages has been updated
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* above:
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*/
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if (pgprot_val(new_prot) == pgprot_val(old_prot)) {
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res = CPA_NO_SPLIT;
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goto out_unlock;
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}
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/*
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* We need to change the attributes. Check, whether we can
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* change the large page in one go. We request a split, when
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* the address is not aligned and the number of pages is
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* smaller than the number of pages in the large page. Note
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* that we limited the number of possible pages already to
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* the number of pages in the large page.
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*/
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if (address == (nextpage_addr - psize) && cpa->numpages == numpages) {
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/*
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* The address is aligned and the number of pages
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* covers the full page.
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*/
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new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));
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__set_pmd_pte(kpte, address, new_pte);
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cpa->flushtlb = 1;
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res = CPA_NO_SPLIT;
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}
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out_unlock:
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spin_unlock_irqrestore(&pgd_lock, flags);
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return res;
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}
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static int split_large_page(pte_t *kpte, unsigned long address)
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{
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pgprot_t ref_prot = pte_pgprot(pte_clrhuge(*kpte));
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@ -295,7 +380,7 @@ out_unlock:
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static int __change_page_attr(unsigned long address, struct cpa_data *cpa)
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{
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struct page *kpte_page;
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int level, err = 0;
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int level, res;
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pte_t *kpte;
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repeat:
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@ -338,13 +423,34 @@ repeat:
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set_pte_atomic(kpte, new_pte);
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cpa->flushtlb = 1;
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}
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} else {
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err = split_large_page(kpte, address);
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if (!err)
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goto repeat;
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cpa->flushtlb = 1;
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cpa->numpages = 1;
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return 0;
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}
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return err;
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/*
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* Check, whether we can keep the large page intact
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* and just change the pte:
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*/
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res = try_preserve_large_page(kpte, address, cpa);
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if (res < 0)
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return res;
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/*
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* When the range fits into the existing large page,
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* return. cp->numpages and cpa->tlbflush have been updated in
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* try_large_page:
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*/
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if (res == CPA_NO_SPLIT)
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return 0;
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/*
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* We have to split the large page:
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*/
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res = split_large_page(kpte, address);
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if (res)
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return res;
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cpa->flushtlb = 1;
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goto repeat;
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}
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/**
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@ -410,15 +516,27 @@ static int change_page_attr_addr(struct cpa_data *cpa)
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static int __change_page_attr_set_clr(struct cpa_data *cpa)
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{
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unsigned int i;
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int ret;
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int ret, numpages = cpa->numpages;
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for (i = 0; i < cpa->numpages ; i++, cpa->vaddr += PAGE_SIZE) {
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while (numpages) {
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/*
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* Store the remaining nr of pages for the large page
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* preservation check.
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*/
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cpa->numpages = numpages;
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ret = change_page_attr_addr(cpa);
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if (ret)
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return ret;
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}
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/*
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* Adjust the number of pages with the result of the
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* CPA operation. Either a large page has been
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* preserved or a single page update happened.
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*/
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BUG_ON(cpa->numpages > numpages);
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numpages -= cpa->numpages;
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cpa->vaddr += cpa->numpages * PAGE_SIZE;
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}
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return 0;
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}
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