| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <tip-eyi25t4eh3l4cd2zp4k3bj6c@git.kernel.org>
Date: Wed, 26 Sep 2012 23:00:43 -0700
From: tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
torvalds@...ux-foundation.org, a.p.zijlstra@...llo.nl,
pjt@...gle.com, riel@...hat.com, akpm@...ux-foundation.org,
tglx@...utronix.de
Subject: [tip:sched/numa] mm/thp: Preserve pgprot across huge page split
Commit-ID: 93c9d633bd9e183f105bc59d798d61c216a514f0
Gitweb: http://git.kernel.org/tip/93c9d633bd9e183f105bc59d798d61c216a514f0
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Tue, 17 Jul 2012 18:25:14 +0200
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 26 Sep 2012 11:48:31 +0200
mm/thp: Preserve pgprot across huge page split
If we marked a THP with our special PROT_NONE protections, ensure we
don't loose them over a split.
Collapse seems to always allocate a new (huge) page which should
already end up on the new target node so loosing protections there
isn't a problem.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Reviewed-by: Rik van Riel <riel@...hat.com>
Cc: Paul Turner <pjt@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Link: http://lkml.kernel.org/n/tip-eyi25t4eh3l4cd2zp4k3bj6c@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
arch/x86/include/asm/pgtable.h | 1 +
mm/huge_memory.c | 104 +++++++++++++++++++---------------------
2 files changed, 50 insertions(+), 55 deletions(-)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 49afb3f..402704f 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -350,6 +350,7 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
}
#define pte_pgprot(x) __pgprot(pte_flags(x) & PTE_FLAGS_MASK)
+#define pmd_pgprot(x) __pgprot(pmd_val(x) & ~_HPAGE_CHG_MASK)
#define canon_pgprot(p) __pgprot(massage_pgprot(p))
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 57c4b93..4a74e34 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1353,64 +1353,60 @@ static int __split_huge_page_map(struct page *page,
int ret = 0, i;
pgtable_t pgtable;
unsigned long haddr;
+ pgprot_t prot;
spin_lock(&mm->page_table_lock);
pmd = page_check_address_pmd(page, mm, address,
PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
- if (pmd) {
- pgtable = get_pmd_huge_pte(mm);
- pmd_populate(mm, &_pmd, pgtable);
-
- for (i = 0, haddr = address; i < HPAGE_PMD_NR;
- i++, haddr += PAGE_SIZE) {
- pte_t *pte, entry;
- BUG_ON(PageCompound(page+i));
- entry = mk_pte(page + i, vma->vm_page_prot);
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- if (!pmd_write(*pmd))
- entry = pte_wrprotect(entry);
- else
- BUG_ON(page_mapcount(page) != 1);
- if (!pmd_young(*pmd))
- entry = pte_mkold(entry);
- pte = pte_offset_map(&_pmd, haddr);
- BUG_ON(!pte_none(*pte));
- set_pte_at(mm, haddr, pte, entry);
- pte_unmap(pte);
- }
+ if (!pmd)
+ goto unlock;
- smp_wmb(); /* make pte visible before pmd */
- /*
- * Up to this point the pmd is present and huge and
- * userland has the whole access to the hugepage
- * during the split (which happens in place). If we
- * overwrite the pmd with the not-huge version
- * pointing to the pte here (which of course we could
- * if all CPUs were bug free), userland could trigger
- * a small page size TLB miss on the small sized TLB
- * while the hugepage TLB entry is still established
- * in the huge TLB. Some CPU doesn't like that. See
- * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
- * Erratum 383 on page 93. Intel should be safe but is
- * also warns that it's only safe if the permission
- * and cache attributes of the two entries loaded in
- * the two TLB is identical (which should be the case
- * here). But it is generally safer to never allow
- * small and huge TLB entries for the same virtual
- * address to be loaded simultaneously. So instead of
- * doing "pmd_populate(); flush_tlb_range();" we first
- * mark the current pmd notpresent (atomically because
- * here the pmd_trans_huge and pmd_trans_splitting
- * must remain set at all times on the pmd until the
- * split is complete for this pmd), then we flush the
- * SMP TLB and finally we write the non-huge version
- * of the pmd entry with pmd_populate.
- */
- set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
- flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
- pmd_populate(mm, pmd, pgtable);
- ret = 1;
+ prot = pmd_pgprot(*pmd);
+ pgtable = get_pmd_huge_pte(mm);
+ pmd_populate(mm, &_pmd, pgtable);
+
+ for (i = 0, haddr = address; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
+ pte_t *pte, entry;
+
+ BUG_ON(PageCompound(page+i));
+ entry = mk_pte(page + i, prot);
+ entry = pte_mkdirty(entry);
+ if (!pmd_young(*pmd))
+ entry = pte_mkold(entry);
+ pte = pte_offset_map(&_pmd, haddr);
+ BUG_ON(!pte_none(*pte));
+ set_pte_at(mm, haddr, pte, entry);
+ pte_unmap(pte);
}
+
+ smp_wmb(); /* make ptes visible before pmd, see __pte_alloc */
+ /*
+ * Up to this point the pmd is present and huge.
+ *
+ * If we overwrite the pmd with the not-huge version, we could trigger
+ * a small page size TLB miss on the small sized TLB while the hugepage
+ * TLB entry is still established in the huge TLB.
+ *
+ * Some CPUs don't like that. See
+ * http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 383
+ * on page 93.
+ *
+ * Thus it is generally safer to never allow small and huge TLB entries
+ * for overlapping virtual addresses to be loaded. So we first mark the
+ * current pmd not present, then we flush the TLB and finally we write
+ * the non-huge version of the pmd entry with pmd_populate.
+ *
+ * The above needs to be done under the ptl because pmd_trans_huge and
+ * pmd_trans_splitting must remain set on the pmd until the split is
+ * complete. The ptl also protects against concurrent faults due to
+ * making the pmd not-present.
+ */
+ set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
+ flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
+ pmd_populate(mm, pmd, pgtable);
+ ret = 1;
+
+unlock:
spin_unlock(&mm->page_table_lock);
return ret;
@@ -2241,9 +2237,7 @@ static int khugepaged_wait_event(void)
static void khugepaged_do_scan(struct page **hpage)
{
unsigned int progress = 0, pass_through_head = 0;
- unsigned int pages = khugepaged_pages_to_scan;
-
- barrier(); /* write khugepaged_pages_to_scan to local stack */
+ unsigned int pages = ACCESS_ONCE(khugepaged_pages_to_scan);
while (progress < pages) {
cond_resched();
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists