Re: [PATCH 02/16] debug_vm_pgtable/ppc64: Avoid setting top bits in radom value

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Le 12/08/2020 à 08:33, Aneesh Kumar K.V a écrit :
ppc64 use bit 62 to indicate a pte entry (_PAGE_PTE). Avoid setting that bit in
random value.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
  mm/debug_vm_pgtable.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 086309fb9b6f..4c32063a8acf 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -45,9 +45,12 @@
   * pxx_clear() because of how dynamic page table folding works on s390. So
   * while loading up the entries do not change the lower 4 bits. It does not
   * have affect any other platform.
+ *
+ * Also avoid the 62nd bit on ppc64 that is used to mark a pte entry.
   */
  #define S390_MASK_BITS	4
-#define RANDOM_ORVALUE	GENMASK(BITS_PER_LONG - 1, S390_MASK_BITS)
+#define PPC_MASK_BITS	2
+#define RANDOM_ORVALUE	GENMASK(BITS_PER_LONG - 1 - PPC_MASK_BITS, S390_MASK_BITS)

Do you mean:

#define RANDOM_ORVALUE GENMASK(BITS_PER_LONG - 1, PPC_MASK_BITS | S390_MASK_BITS)

Christophe

  #define RANDOM_NZVALUE	GENMASK(7, 0)
static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot)






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