Re: [PATCH 2/2] iommu/dma: Respect IOMMU aperture when allocating

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

On Tue, Aug 09, 2016 at 04:23:18PM +0100, Robin Murphy wrote:
> Where a device driver has set a 64-bit DMA mask to indicate the absence
> of addressing limitations, we still need to ensure that we don't
> allocate IOVAs beyond the actual input size of the IOMMU. The reported
> aperture is the most reliable way we have of inferring that input
> address size, so use that to enforce a hard upper limit.
> 
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>

Also missing 'Fixes:' line.

> ---
> 
> This is the only other thing I currently have which could perhaps be
> considered a fix; otherwise I'll pull it into the PCI/SMMU series.
> 
>  drivers/iommu/dma-iommu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 7d991c81c4fa..092d781f5f35 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -158,6 +158,8 @@ static struct iova *__alloc_iova(struct iova_domain *iovad, size_t size,
>  	unsigned long shift = iova_shift(iovad);
>  	unsigned long length = iova_align(iovad, size) >> shift;
>  
> +	if (domain->geometry.force_aperture)
> +		dma_limit &= domain->geometry.aperture_end;

This might work, but is misleading as limits and aperture_end are
neither a mask nor a bitfield. It is more descriptive to use min()
here:

	dma_limit = min(dma_limit, omain->geometry.aperture_end);