On 9/2/20 9:19 AM, Anshuman Khandual wrote:
On 09/01/2020 03:28 PM, Aneesh Kumar K.V wrote:
On 9/1/20 1:08 PM, Anshuman Khandual wrote:
On 09/01/2020 12:07 PM, Aneesh Kumar K.V wrote:
On 9/1/20 8:55 AM, Anshuman Khandual wrote:
On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
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 <aneesh.kumar@xxxxxxxxxxxxx>
---
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.
and also fetch the pte value which is used further.
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()
and fetch the old value set previously.
In that case, please move above two lines i.e
pte = pfn_pte(pte_aligned, prot);
set_pte_at(mm, vaddr, ptep, pte);
from debug_vm_pgtable() to pte_clear_tests() and update it's arguments
as required.
Frankly, I don't understand what these tests are testing. It all looks like some random clear and set.
The idea here is to have some value with some randomness preferably, in
a given PTEP before attempting to clear the entry, in order to make sure
that pte_clear() is indeed clearing something of non-zero value.
static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,
unsigned long vaddr, unsigned long pfn,
pgprot_t prot)
{
pte_t pte = pfn_pte(pfn, prot);
set_pte_at(mm, vaddr, ptep, pte);
pte = ptep_get_and_clear(mm, vaddr, ptep);
Looking at this again, this preceding pfn_pte() followed by set_pte_at()
is not really required. Its reasonable to start with what ever was there
in the PTEP as a seed value which anyway gets added with RANDOM_ORVALUE.
s/ptep_get/ptep_get_and_clear is sufficient to take care of the powerpc
set_pte_at() constraint.
But the way test is written we had none pte before. That is why I added
that set_pte_at to put something there. With none pte the below sequence
fails.
pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
set_pte_at(mm, vaddr, ptep, pte);
because nobody is marking a _PAGE_PTE there.
pte_t pte = pfn_pte(pfn, prot);
pr_debug("Validating PTE clear\n");
pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
set_pte_at(mm, vaddr, ptep, pte);
barrier();
pte_clear(mm, vaddr, ptep);
pte = ptep_get(ptep);
WARN_ON(!pte_none(pte));
will that work for you?
-aneesh
