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    SubjectRe: [PATCH v7 01/19] iommu/dma: Implement PCI allocation optimisation
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    On 09/01/17 13:45, Eric Auger wrote:
    > From: Robin Murphy <robin.murphy@arm.com>
    >
    > Whilst PCI devices may have 64-bit DMA masks, they still benefit from
    > using 32-bit addresses wherever possible in order to avoid DAC (PCI) or
    > longer address packets (PCIe), which may incur a performance overhead.
    > Implement the same optimisation as other allocators by trying to get a
    > 32-bit address first, only falling back to the full mask if that fails.

    Oops, this was just some development work which got promoted to my misc
    branch for safe keeping; it really has nothing to do with this series.

    I'd managed to overlook that one of the __alloc_iova() conflicts hit the
    MSI cookie patch, sorry. Things are now in a more appropriate order in
    my tree.

    Robin.

    > Signed-off-by: Robin Murphy <robin.murphy@arm.com>
    > ---
    > drivers/iommu/dma-iommu.c | 21 +++++++++++++++------
    > 1 file changed, 15 insertions(+), 6 deletions(-)
    >
    > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
    > index 2db0d64..a59ca47 100644
    > --- a/drivers/iommu/dma-iommu.c
    > +++ b/drivers/iommu/dma-iommu.c
    > @@ -204,19 +204,28 @@ int dma_direction_to_prot(enum dma_data_direction dir, bool coherent)
    > }
    >
    > static struct iova *__alloc_iova(struct iommu_domain *domain, size_t size,
    > - dma_addr_t dma_limit)
    > + dma_addr_t dma_limit, struct device *dev)
    > {
    > struct iova_domain *iovad = cookie_iovad(domain);
    > unsigned long shift = iova_shift(iovad);
    > unsigned long length = iova_align(iovad, size) >> shift;
    > + struct iova *iova = NULL;
    >
    > if (domain->geometry.force_aperture)
    > dma_limit = min(dma_limit, domain->geometry.aperture_end);
    > +
    > + /* Try to get PCI devices a SAC address */
    > + if (dma_limit > DMA_BIT_MASK(32) && dev_is_pci(dev))
    > + iova = alloc_iova(iovad, length, DMA_BIT_MASK(32) >> shift,
    > + true);
    > /*
    > * 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);
    > + if (!iova)
    > + iova = alloc_iova(iovad, length, dma_limit >> shift, true);
    > +
    > + return iova;
    > }
    >
    > /* The IOVA allocator knows what we mapped, so just unmap whatever that was */
    > @@ -369,7 +378,7 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
    > if (!pages)
    > return NULL;
    >
    > - iova = __alloc_iova(domain, size, dev->coherent_dma_mask);
    > + iova = __alloc_iova(domain, size, dev->coherent_dma_mask, dev);
    > if (!iova)
    > goto out_free_pages;
    >
    > @@ -440,7 +449,7 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
    > struct iova_domain *iovad = cookie_iovad(domain);
    > size_t iova_off = iova_offset(iovad, phys);
    > size_t len = iova_align(iovad, size + iova_off);
    > - struct iova *iova = __alloc_iova(domain, len, dma_get_mask(dev));
    > + struct iova *iova = __alloc_iova(domain, len, dma_get_mask(dev), dev);
    >
    > if (!iova)
    > return DMA_ERROR_CODE;
    > @@ -598,7 +607,7 @@ int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
    > prev = s;
    > }
    >
    > - iova = __alloc_iova(domain, iova_len, dma_get_mask(dev));
    > + iova = __alloc_iova(domain, iova_len, dma_get_mask(dev), dev);
    > if (!iova)
    > goto out_restore_sg;
    >
    > @@ -675,7 +684,7 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
    > if (!msi_page)
    > return NULL;
    >
    > - iova = __alloc_iova(domain, iovad->granule, dma_get_mask(dev));
    > + iova = __alloc_iova(domain, iovad->granule, dma_get_mask(dev), dev);
    > if (!iova)
    > goto out_free_page;
    >
    >

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