On 09/18/2019 11:52 PM, Gerald Schaefer wrote: > On Wed, 18 Sep 2019 18:26:03 +0200 > Christophe Leroy <christophe.leroy@xxxxxx> wrote: > > [..] >> My suggestion was not to completely drop the #ifdef but to do like you >> did in pgd_clear_tests() for instance, ie to add the following test on >> top of the function: >> >> if (mm_pud_folded(mm) || is_defined(__ARCH_HAS_5LEVEL_HACK)) >> return; >> > > Ah, very nice, this would also fix the remaining issues for s390. Since > we have dynamic page table folding, neither __PAGETABLE_PXX_FOLDED nor > __ARCH_HAS_XLEVEL_HACK is defined, but mm_pxx_folded() will work. Like Christophe mentioned earlier on the other thread, we will convert all __PGTABLE_PXX_FOLDED checks as mm_pxx_folded() but looks like ARCH_HAS_[4 and 5]LEVEL_HACK macros will still be around. Will respin the series with all agreed upon changes first and probably we can then discuss pending issues from there. > > mm_alloc() returns with a 3-level page table by default on s390, so we > will run into issues in p4d_clear/populate_tests(), and also at the end > with p4d/pud_free() (double free). > > So, adding the mm_pud_folded() check to p4d_clear/populate_tests(), > and also adding mm_p4d/pud_folded() checks at the end before calling> p4d/pud_free(), would make it all work on s390. Atleast p4d_clear/populate_tests() tests will be taken care. > > BTW, regarding p4d/pud_free(), I'm not sure if we should rather check > the folding inside our s390 functions, similar to how we do it for > p4d/pud_free_tlb(), instead of relying on not being called for folded > p4d/pud. So far, I see no problem with this behavior, all callers of > p4d/pud_free() should be fine because of our folding check within > p4d/pud_present/none(). But that doesn't mean that it is correct not > to check for the folding inside p4d/pud_free(). At least, with this > test module we do now have a caller of p4d/pud_free() on potentially > folded entries, so instead of adding pxx_folded() checks to this > test module, we could add them to our p4d/pud_free() functions. > Any thoughts on this? Agreed, it seems better to do the check inside p4d/pud_free() functions.
