Hi Marek, On 07/11/16 13:06, Marek Szyprowski wrote: > When one called iommu_dma_init_domain() with size smaller than device's > DMA mask, the alloc_iova() will not respect it and always assume that all > IOVA addresses will be allocated from the the (base ... dev->dma_mask) range.
Is that actually a problem for anything? > This patch fixes this issue by taking the configured address space size > parameter into account (if it is smaller than the device's dma_mask). TBH I've been pondering ripping the size stuff out of dma-iommu, as it all stems from me originally failing to understand what dma_32bit_pfn is actually for. The truth is that iova_domains just don't have a size or upper limit; however if devices with both large and small DMA masks share a domain, then the top-down nature of the allocator means that allocating for the less-capable devices would involve walking through every out-of-range entry in the tree every time. Having cached32_node based on dma_32bit_pfn just provides an optimised starting point for searching within the smaller mask. Would it hurt any of your use-cases to relax/rework the reinitialisation checks in iommu_dma_init_domain()? Alternatively if we really do have a case for wanting a hard upper limit, it might make more sense to add an end_pfn to the iova_domain and handle it in the allocator itself. Robin. > Signed-off-by: Marek Szyprowski <[email protected]> > --- > drivers/iommu/dma-iommu.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index c5ab8667e6f2..8b4b72654359 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -212,11 +212,13 @@ static struct iova *__alloc_iova(struct iommu_domain > *domain, size_t size, > > if (domain->geometry.force_aperture) > dma_limit = min(dma_limit, domain->geometry.aperture_end); > + > + dma_limit = min(dma_limit >> shift, (dma_addr_t)iovad->dma_32bit_pfn); > /* > * Enforce size-alignment to be safe - there could perhaps be an > * attribute to control this per-device, or at least per-domain... > */ > - return alloc_iova(iovad, length, dma_limit >> shift, true); > + return alloc_iova(iovad, length, dma_limit, true); > } > > /* The IOVA allocator knows what we mapped, so just unmap whatever that was > */ >
