From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>, npiggin@gmail.com
Subject: [PATCH v4 03/22] powerpc/mm/hash64: use _PAGE_PTE when checking for pte_present
Date: Tue, 5 May 2020 12:47:10 +0530 [thread overview]
Message-ID: <20200505071729.54912-4-aneesh.kumar@linux.ibm.com> (raw)
In-Reply-To: <20200505071729.54912-1-aneesh.kumar@linux.ibm.com>
This makes the pte_present check stricter by checking for additional _PAGE_PTE
bit. A level 1 pte pointer (THP pte) can be switched to a pointer to level 0 pte
page table page by following two operations.
1) THP split.
2) madvise(MADV_DONTNEED) in parallel to page fault.
A lockless page table walk need to make sure we can handle such changes
gracefully.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
arch/powerpc/include/asm/book3s/64/pgtable.h | 15 ++++++++++-----
arch/powerpc/mm/book3s64/hash_utils.c | 11 +++++++++--
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 368b136517e0..03521a8b0292 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -553,6 +553,12 @@ static inline pte_t pte_clear_savedwrite(pte_t pte)
}
#endif /* CONFIG_NUMA_BALANCING */
+static inline bool pte_hw_valid(pte_t pte)
+{
+ return (pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE)) ==
+ cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE);
+}
+
static inline int pte_present(pte_t pte)
{
/*
@@ -561,12 +567,11 @@ static inline int pte_present(pte_t pte)
* invalid during ptep_set_access_flags. Hence we look for _PAGE_INVALID
* if we find _PAGE_PRESENT cleared.
*/
- return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_INVALID));
-}
-static inline bool pte_hw_valid(pte_t pte)
-{
- return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT));
+ if (pte_hw_valid(pte))
+ return true;
+ return (pte_raw(pte) & cpu_to_be64(_PAGE_INVALID | _PAGE_PTE)) ==
+ cpu_to_be64(_PAGE_INVALID | _PAGE_PTE);
}
#ifdef CONFIG_PPC_MEM_KEYS
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index e951e87a974d..525eac4ee2c2 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1350,8 +1350,15 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
goto bail;
}
- /* Add _PAGE_PRESENT to the required access perm */
- access |= _PAGE_PRESENT;
+ /*
+ * Add _PAGE_PRESENT to the required access perm. If there are parallel
+ * updates to the pte that can possibly clear _PAGE_PTE, catch that too.
+ *
+ * We can safely use the return pte address in rest of the function
+ * because we do set H_PAGE_BUSY which prevents further updates to pte
+ * from generic code.
+ */
+ access |= _PAGE_PRESENT | _PAGE_PTE;
/*
* Pre-check access permissions (will be re-checked atomically
--
2.26.2
next prev parent reply other threads:[~2020-05-05 7:32 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 7:17 [PATCH v4 00/22] Avoid IPI while updating page table entries Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 01/22] powerpc/pkeys: Avoid using lockless page table walk Aneesh Kumar K.V
2020-05-13 8:49 ` Michael Ellerman
2020-05-05 7:17 ` [PATCH v4 02/22] powerpc/pkeys: Check vma before returning key fault error to the user Aneesh Kumar K.V
2020-05-05 7:17 ` Aneesh Kumar K.V [this message]
2020-05-05 7:17 ` [PATCH v4 04/22] powerpc/hash64: Restrict page table lookup using init_mm with __flush_hash_table_range Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 05/22] powerpc/book3s64/hash: Use the pte_t address from the caller Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 06/22] powerpc/mce: Don't reload pte val in addr_to_pfn Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 07/22] powerpc/perf/callchain: Use __get_user_pages_fast in read_user_stack_slow Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 08/22] powerpc/kvm/book3s: switch from raw_spin_*lock to arch_spin_lock Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 09/22] powerpc/kvm/book3s: Add helper to walk partition scoped linux page table Aneesh Kumar K.V
2020-05-28 1:43 ` Paul Mackerras
2020-05-28 6:01 ` Aneesh Kumar K.V
2020-05-28 7:25 ` Paul Mackerras
2020-05-05 7:17 ` [PATCH v4 10/22] powerpc/kvm/nested: Add helper to walk nested shadow " Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 11/22] powerpc/kvm/book3s: Use kvm helpers to walk shadow or secondary table Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 12/22] powerpc/kvm/book3s: Add helper for host page table walk Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 13/22] powerpc/kvm/book3s: Use find_kvm_host_pte in page fault handler Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 14/22] powerpc/kvm/book3s: Use find_kvm_host_pte in h_enter Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 15/22] powerpc/kvm/book3s: use find_kvm_host_pte in pute_tce functions Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 16/22] powerpc/kvm/book3s: Avoid using rmap to protect parallel page table update Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 17/22] powerpc/kvm/book3s: use find_kvm_host_pte in kvmppc_book3s_instantiate_page Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 18/22] powerpc/kvm/book3s: Use find_kvm_host_pte in kvmppc_get_hpa Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 19/22] powerpc/kvm/book3s: Use pte_present instead of opencoding _PAGE_PRESENT check Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 20/22] powerpc/mm/book3s64: Avoid sending IPI on clearing PMD Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 21/22] mm: change pmdp_huge_get_and_clear_full take vm_area_struct as arg Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 22/22] powerpc/mm/book3s64: Fix MADV_DONTNEED and parallel page fault race Aneesh Kumar K.V
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