On 05/08/16 17:00, Michael Ellerman wrote: > Alexey Kardashevskiy <a...@ozlabs.ru> writes: > >> In some situations the userspace memory context may live longer than >> the userspace process itself so if we need to do proper memory context >> cleanup, we better cache @mm and use it later when the process is gone >> (@current or @current->mm are NULL). >> >> This changes mm_iommu_xxx API to receive mm_struct instead of using one >> from @current. >> >> This is needed by the following patch to do proper cleanup in time. >> This depends on "powerpc/powernv/ioda: Fix endianness when reading TCEs" >> to do proper cleanup via tce_iommu_clear() patch. >> >> To keep API consistent, this replaces mm_context_t with mm_struct; >> we stick to mm_struct as mm_iommu_adjust_locked_vm() helper needs >> access to &mm->mmap_sem. >> >> This should cause no behavioral change. > > Is this a theoretical bug, or do we hit it in practice?
Actual bug. > > In other words, should I merge this as a fix for 4.8, or can it wait for > 4.9 with the rest of the series? Assuming this does not have "rb" or "ab" from anyone familiar with IOMMU on powernv, this has to wait :-/ > >> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> >> --- >> arch/powerpc/include/asm/mmu_context.h | 20 +++++++------ >> arch/powerpc/kernel/setup-common.c | 2 +- >> arch/powerpc/mm/mmu_context_book3s64.c | 4 +-- >> arch/powerpc/mm/mmu_context_iommu.c | 54 >> ++++++++++++++-------------------- > >> drivers/vfio/vfio_iommu_spapr_tce.c | 41 ++++++++++++++++---------- > > I'd need an ACK from Alex for that part. -- Alexey
