[PATCH] x86: avoid unnecessary low zone allocation in AMD IOMMU'salloc_coherent

[FUJITA Tomonori]

This is for tip/iommu.

btw, Joery, what happens if map_sg (or map_single) gets
not-DMA-capable buffer in the case of !iommu || !domain?


==
From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Subject: [PATCH] x86: avoid unnecessary low zone allocation in AMD IOMMU's alloc_coherent

x86's common alloc_coherent (dma_alloc_coherent in dma-mapping.h) sets
up the gfp flag according to the device dma_mask but AMD IOMMU doesn't
need it for devices that the IOMMU can do virtual mappings for. This
patch avoids unnecessary low zone allocation.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
---
 arch/x86/kernel/amd_iommu.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 01c68c3..8efd249 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -999,6 +999,11 @@ static void *alloc_coherent(struct device *dev, size_t size,
 	u16 devid;
 	phys_addr_t paddr;
 
+	get_device_resources(dev, &iommu, &domain, &devid);
+
+	if (iommu && domain)
+		flag &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
+
 	virt_addr = (void *)__get_free_pages(flag, get_order(size));
 	if (!virt_addr)
 		return 0;
@@ -1006,8 +1011,6 @@ static void *alloc_coherent(struct device *dev, size_t size,
 	memset(virt_addr, 0, size);
 	paddr = virt_to_phys(virt_addr);
 
-	get_device_resources(dev, &iommu, &domain, &devid);
-
 	if (!iommu || !domain) {
 		*dma_addr = (dma_addr_t)paddr;
 		return virt_addr;
-- 
1.5.4.2

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