[PATCH v3 03/13] mm/debug_vm_pgtable/ppc64: Avoid setting top bits in radom value

[Anshuman Khandual]

On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
> 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 at linux.ibm.com>
> ---
>  mm/debug_vm_pgtable.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 086309fb9b6f..bbf9df0e64c6 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -44,10 +44,17 @@
>   * entry type. But these bits might affect the ability to clear entries with
>   * 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.
> + * 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 S390_SKIP_MASK		GENMASK(3, 0)
> +#ifdef CONFIG_PPC_BOOK3S_64
> +#define PPC64_SKIP_MASK		GENMASK(62, 62)
> +#else
> +#define PPC64_SKIP_MASK		0x0
> +#endif

Please drop the #ifdef CONFIG_PPC_BOOK3S_64 here. We already accommodate skip
bits for a s390 platform requirement and can also do so for ppc64 as well. As
mentioned before, please avoid adding any platform specific constructs in the
test.

> +#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
> +#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
>  #define RANDOM_NZVALUE	GENMASK(7, 0)

Please fix the alignments here. Feel free to consider following changes after
this patch.

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 122416464e0f..f969031152bb 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -48,14 +48,11 @@
  * have affect any other platform. Also avoid the 62nd bit on ppc64 that is
  * used to mark a pte entry.
  */
-#define S390_SKIP_MASK         GENMASK(3, 0)
-#ifdef CONFIG_PPC_BOOK3S_64
-#define PPC64_SKIP_MASK                GENMASK(62, 62)
-#else
-#define PPC64_SKIP_MASK                0x0
-#endif
-#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
-#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
+#define S390_SKIP_MASK GENMASK(3, 0)
+#define PPC64_SKIP_MASK        GENMASK(62, 62)
+#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
+#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
+
 #define RANDOM_NZVALUE GENMASK(7, 0)
 
>  
>  static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot)
> 

Besides, there is also one checkpatch.pl warning here.

WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#7: 
ppc64 use bit 62 to indicate a pte entry (_PAGE_PTE). Avoid setting that bit in

total: 0 errors, 1 warnings, 20 lines checked