On 07/16/2020 07:44 PM, Steven Price wrote:
> On 13/07/2020 04:23, Anshuman Khandual wrote:
>> This adds new tests validating arch page table helpers for these following
>> core memory features. These tests create and test specific mapping types at
>> various page table levels.
>>
>> 1. SPECIAL mapping
>> 2. PROTNONE mapping
>> 3. DEVMAP mapping
>> 4. SOFTDIRTY mapping
>> 5. SWAP mapping
>> 6. MIGRATION mapping
>> 7. HUGETLB mapping
>> 8. THP mapping
>>
>> Cc: Andrew Morton <[email protected]>
>> Cc: Gerald Schaefer <[email protected]>
>> Cc: Christophe Leroy <[email protected]>
>> Cc: Mike Rapoport <[email protected]>
>> Cc: Vineet Gupta <[email protected]>
>> Cc: Catalin Marinas <[email protected]>
>> Cc: Will Deacon <[email protected]>
>> Cc: Benjamin Herrenschmidt <[email protected]>
>> Cc: Paul Mackerras <[email protected]>
>> Cc: Michael Ellerman <[email protected]>
>> Cc: Heiko Carstens <[email protected]>
>> Cc: Vasily Gorbik <[email protected]>
>> Cc: Christian Borntraeger <[email protected]>
>> Cc: Thomas Gleixner <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: Borislav Petkov <[email protected]>
>> Cc: "H. Peter Anvin" <[email protected]>
>> Cc: Kirill A. Shutemov <[email protected]>
>> Cc: Paul Walmsley <[email protected]>
>> Cc: Palmer Dabbelt <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Tested-by: Vineet Gupta <[email protected]> #arc
>> Reviewed-by: Zi Yan <[email protected]>
>> Suggested-by: Catalin Marinas <[email protected]>
>> Signed-off-by: Anshuman Khandual <[email protected]>
>> ---
>> mm/debug_vm_pgtable.c | 302 +++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 301 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index 61ab16fb2e36..2fac47db3eb7 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
> [...]
>> +
>> +static void __init pte_swap_tests(unsigned long pfn, pgprot_t prot)
>> +{
>> + swp_entry_t swp;
>> + pte_t pte;
>> +
>> + pte = pfn_pte(pfn, prot);
>> + swp = __pte_to_swp_entry(pte);
>
> Minor issue: this doesn't look necessarily valid - there's no reason a normal
> PTE can be turned into a swp_entry. In practise this is likely to work on all
> architectures because there's no reason not to use (at least) all the PFN
> bits for the swap entry, but it doesn't exactly seem correct.
Agreed, that it is a simple test but nonetheless a valid one which
makes sure that PFN value remained unchanged during pte <---> swp
conversion.
>
> Can we start with a swp_entry_t (from __swp_entry()) and check the round trip
> of that?
>
> It would also seem sensible to have a check that
> is_swap_pte(__swp_entry_to_pte(__swp_entry(x,y))) is true.
>From past experiences, getting any these new tests involving platform
helpers, working on all existing enabled archs is neither trivial nor
going to be quick. Existing tests here are known to succeed in enabled
platforms. Nonetheless, proposed tests as in the above suggestions do
make sense but will try to accommodate them in a later patch.
