On 17/10/2018 12:00, David Gibson wrote: > On Mon, Oct 15, 2018 at 08:24:15PM +1100, Alexey Kardashevskiy wrote: >> Since we are going to have 2 different preregistering helpers, let's >> make it clear that mm_iommu_new() is only for the normal (i.e. not device) >> memory and for existing areas mm_iommu_get() should be used instead. >> >> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx> > > I think the idea is sensible. However (and, yes, this is really an > existing bug) - shouldn't we check for a request to add anything > overlapping with an existing region, not just one that exactly > matches? The overlap check is below the changed hunk: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/mm/mmu_context_iommu.c#n150 > >> --- >> arch/powerpc/mm/mmu_context_iommu.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c >> index a8c4a3c..839dbce 100644 >> --- a/arch/powerpc/mm/mmu_context_iommu.c >> +++ b/arch/powerpc/mm/mmu_context_iommu.c >> @@ -141,8 +141,7 @@ long mm_iommu_new(struct mm_struct *mm, unsigned long ua, unsigned long entries, >> list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, >> next) { >> if ((mem->ua == ua) && (mem->entries == entries)) { >> - ++mem->used; >> - *pmem = mem; >> + ret = -EBUSY; >> goto unlock_exit; >> } >> > -- Alexey
