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

[Christophe Leroy]

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 at linux.ibm.com>
> ---
>   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)
>