Re: [PATCH v3 06/13] mm/debug_vm_pgtable/THP: Mark the pte entry huge before using set_pmd/pud_at

"Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> · Tue, 1 Sep 2020 11:53:02 +0530

On 9/1/20 8:51 AM, Anshuman Khandual wrote:


On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
kernel expects entries to be marked huge before we use set_pmd_at()/set_pud_at().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
  mm/debug_vm_pgtable.c | 21 ++++++++++++---------
  1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 5c0680836fe9..de83a20c1b30 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -155,7 +155,7 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
  				      unsigned long pfn, unsigned long vaddr,
  				      pgprot_t prot)
  {
-	pmd_t pmd = pfn_pmd(pfn, prot);
+	pmd_t pmd;
  
  	if (!has_transparent_hugepage())
  		return;
@@ -164,19 +164,19 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
  	/* Align the address wrt HPAGE_PMD_SIZE */
  	vaddr = (vaddr & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
  
-	pmd = pfn_pmd(pfn, prot);
+	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
  	set_pmd_at(mm, vaddr, pmdp, pmd);
  	pmdp_set_wrprotect(mm, vaddr, pmdp);
  	pmd = READ_ONCE(*pmdp);
  	WARN_ON(pmd_write(pmd));
  
-	pmd = pfn_pmd(pfn, prot);
+	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
  	set_pmd_at(mm, vaddr, pmdp, pmd);
  	pmdp_huge_get_and_clear(mm, vaddr, pmdp);
  	pmd = READ_ONCE(*pmdp);
  	WARN_ON(!pmd_none(pmd));
  
-	pmd = pfn_pmd(pfn, prot);
+	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
  	pmd = pmd_wrprotect(pmd);
  	pmd = pmd_mkclean(pmd);
  	set_pmd_at(mm, vaddr, pmdp, pmd);
@@ -237,7 +237,7 @@ static void __init pmd_huge_tests(pmd_t *pmdp, unsigned long pfn, pgprot_t prot)
  
  static void __init pmd_savedwrite_tests(unsigned long pfn, pgprot_t prot)
  {
-	pmd_t pmd = pfn_pmd(pfn, prot);
+	pmd_t pmd = pmd_mkhuge(pfn_pmd(pfn, prot));

There is no set_pmd_at() in this particular test, why change ?


because if you are building a hugepage you should use pmd_mkhuge(). That 
is what is setting _PAGE_PTE with this series. We don't make pfn_pmd set 
_PAGE_PTE


-aneesh






