Re: [PATCH kernel 3/4] powerpc/mm/iommu: Make mm_iommu_new() fail on existing regions
From: David Gibson <hidden>
Date: 2018-10-17 02:31:48
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 <redacted>
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?
quoted hunk ↗ jump to hunk
--- 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; }
-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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