From: Pasha Tatashin <pasha.tatashin@soleen.com>
To: pasha.tatashin@soleen.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-doc@vger.kernel.org,
akpm@linux-foundation.org, rientjes@google.com, pjt@google.com,
weixugc@google.com, gthelen@google.com, mingo@redhat.com,
corbet@lwn.net, will@kernel.org, rppt@kernel.org,
keescook@chromium.org, tglx@linutronix.de, peterz@infradead.org,
masahiroy@kernel.org, samitolvanen@google.com,
dave.hansen@linux.intel.com, x86@kernel.org, frederic@kernel.org,
hpa@zytor.com, aneesh.kumar@linux.ibm.com
Subject: [RFC 1/3] mm: ptep_clear() page table helper
Date: Tue, 16 Nov 2021 22:00:36 +0000 [thread overview]
Message-ID: <20211116220038.116484-2-pasha.tatashin@soleen.com> (raw)
In-Reply-To: <20211116220038.116484-1-pasha.tatashin@soleen.com>
We have ptep_get_and_clear() and ptep_get_and_clear_full() helpers to
clear PTE from user page tables, but there is no variant for simple
clear of a present PTE from user page tables without using a low level
pte_clear() which can be either native or para-virtualised.
Add a new ptep_clear() that can be used in common code to clear PTEs
from page table. We will need this call later in order to add a hook
for page table check.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
Documentation/vm/arch_pgtable_helpers.rst | 6 ++++--
include/linux/pgtable.h | 8 ++++++++
mm/khugepaged.c | 12 ++----------
3 files changed, 14 insertions(+), 12 deletions(-)
diff --git a/Documentation/vm/arch_pgtable_helpers.rst b/Documentation/vm/arch_pgtable_helpers.rst
index 552567d863b8..fbe06ec75370 100644
--- a/Documentation/vm/arch_pgtable_helpers.rst
+++ b/Documentation/vm/arch_pgtable_helpers.rst
@@ -66,9 +66,11 @@ PTE Page Table Helpers
+---------------------------+--------------------------------------------------+
| pte_mknotpresent | Invalidates a mapped PTE |
+---------------------------+--------------------------------------------------+
-| ptep_get_and_clear | Clears a PTE |
+| ptep_clear | Clears a PTE |
+---------------------------+--------------------------------------------------+
-| ptep_get_and_clear_full | Clears a PTE |
+| ptep_get_and_clear | Clears and returns PTE |
++---------------------------+--------------------------------------------------+
+| ptep_get_and_clear_full | Clears and returns PTE (batched PTE unmap) |
+---------------------------+--------------------------------------------------+
| ptep_test_and_clear_young | Clears young from a PTE |
+---------------------------+--------------------------------------------------+
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index e24d2c992b11..bc8713a76e03 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -258,6 +258,14 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif
+#ifndef __HAVE_ARCH_PTEP_CLEAR
+static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep)
+{
+ pte_clear(mm, addr, ptep);
+}
+#endif
+
#ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long address,
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5f02fda6f265..6ae659ef7e08 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -756,11 +756,7 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
* ptl mostly unnecessary.
*/
spin_lock(ptl);
- /*
- * paravirt calls inside pte_clear here are
- * superfluous.
- */
- pte_clear(vma->vm_mm, address, _pte);
+ ptep_clear(vma->vm_mm, address, _pte);
spin_unlock(ptl);
}
} else {
@@ -774,11 +770,7 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
* inside page_remove_rmap().
*/
spin_lock(ptl);
- /*
- * paravirt calls inside pte_clear here are
- * superfluous.
- */
- pte_clear(vma->vm_mm, address, _pte);
+ ptep_clear(vma->vm_mm, address, _pte);
page_remove_rmap(src_page, false);
spin_unlock(ptl);
free_page_and_swap_cache(src_page);
--
2.34.0.rc1.387.gb447b232ab-goog
next prev parent reply other threads:[~2021-11-16 22:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-16 22:00 [RFC 0/3] page table check Pasha Tatashin
2021-11-16 22:00 ` Pasha Tatashin [this message]
2021-11-17 8:51 ` [RFC 1/3] mm: ptep_clear() page table helper Anshuman Khandual
2021-11-17 16:43 ` Pasha Tatashin
2021-11-16 22:00 ` [RFC 2/3] mm: page table check Pasha Tatashin
2021-11-17 8:08 ` Jonathan Corbet
2021-11-17 16:47 ` Pasha Tatashin
2021-11-16 22:00 ` [RFC 3/3] x86: mm: add x86_64 support for " Pasha Tatashin
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