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Commit 122fac03 authored by Robin Murphy's avatar Robin Murphy Committed by Joerg Roedel
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iommu/dma: Implement PCI allocation optimisation 



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.

Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent f51d7bb7

drivers/iommu/dma-iommu.c

+15 −6
Original line number Diff line number Diff line
@@ -287,19 +287,28 @@ int dma_info_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 */
@@ -452,7 +461,7 @@ 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;
@@ -523,7 +532,7 @@ 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;
@@ -681,7 +690,7 @@ 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;
@@ -761,7 +770,7 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev, 


	msi_page->phys = msi_addr;

	if (iovad) {

		iova = __alloc_iova(domain, size, dma_get_mask(dev));

		iova = __alloc_iova(domain, size, dma_get_mask(dev), dev);

		if (!iova)

			goto out_free_page;

		msi_page->iova = iova_dma_addr(iovad, iova);