Re: [PATCH v3 13/13] mm/debug_vm_pgtable: populate a pte entry before fetching it
From: Anshuman Khandual <hidden>
Date: 2020-09-01 03:26:36
Also in:
linux-arch, linux-mm, linux-s390, linuxppc-dev
On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
quoted hunk ↗ jump to hunk
pte_clear_tests operate on an existing pte entry. Make sure that is not a none pte entry. Signed-off-by: Aneesh Kumar K.V <redacted> --- mm/debug_vm_pgtable.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index 21329c7d672f..8527ebb75f2c 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c@@ -546,7 +546,7 @@ static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp, static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep, unsigned long vaddr) { - pte_t pte = ptep_get(ptep); + pte_t pte = ptep_get_and_clear(mm, vaddr, ptep);
Seems like ptep_get_and_clear() here just clears the entry in preparation for a following set_pte_at() which otherwise would have been a problem on ppc64 as you had pointed out earlier i.e set_pte_at() should not update an existing valid entry. So the commit message here is bit misleading.
quoted hunk ↗ jump to hunk
pr_debug("Validating PTE clear\n"); pte = __pte(pte_val(pte) | RANDOM_ORVALUE);@@ -944,7 +944,7 @@ static int __init debug_vm_pgtable(void) p4d_t *p4dp, *saved_p4dp; pud_t *pudp, *saved_pudp; pmd_t *pmdp, *saved_pmdp, pmd; - pte_t *ptep; + pte_t *ptep, pte; pgtable_t saved_ptep; pgprot_t prot, protnone; phys_addr_t paddr;@@ -1049,6 +1049,8 @@ static int __init debug_vm_pgtable(void) */ ptep = pte_alloc_map_lock(mm, pmdp, vaddr, &ptl); + pte = pfn_pte(pte_aligned, prot); + set_pte_at(mm, vaddr, ptep, pte);
Not here, creating and populating an entry must be done in respective test functions itself. Besides, this seems bit redundant as well. The test pte_clear_tests() with the above change added, already - Clears the PTEP entry with ptep_get_and_clear() - Creates and populates the PTEP with set_pte_at() - Clears with pte_clear() - Checks for pte_none() If the objective is to clear the PTEP entry before calling set_pte_at(), then only the first chunk is required and it should also be merged with a previous patch. [PATCH v3 07/13] mm/debug_vm_pgtable/set_pte/pmd/pud: Don't use set_*_at to update an existing pte entry
pte_clear_tests(mm, ptep, vaddr); pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot); pte_unmap_unlock(ptep, ptl);
There is a checkpatch.pl warning here. WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line) #7: pte_clear_tests operate on an existing pte entry. Make sure that is not a none total: 0 errors, 1 warnings, 24 lines checked There is also a build failure on x86 reported from kernel test robot. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel