linux-kernel - Re: [PATCH] x86: avoid unnecessary low zone allocation in AMD IOMMU's alloc

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Date:	Thu, 11 Sep 2008 11:10:00 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC:	joro@...tes.org, linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [PATCH] x86: avoid unnecessary low zone allocation in AMD IOMMU's alloc_coherent

On Wed, Sep 10, 2008 at 11:45:34PM +0900, FUJITA Tomonori wrote:
> On Wed, 10 Sep 2008 16:38:18 +0200
> Joerg Roedel <joro@...tes.org> wrote:
> > Ok, thats a valid point. I queue your patch with the AMD IOMMU updates
> > for 2.6.28. Thanks.
> 
> Ingo already has queued it his tree, I think.

I asked Ingo to remove it from his tree to avoid merge conflicts with
updates I am currently preparing. Here is the patch I queued into my
2.6.28 update chain.

Joerg

===
commit 42a7fa8d8a7f1680cba76e4824dba30bfd1c9d70
Author: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Date:   Wed Sep 10 20:19:40 2008 +0900

    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@....ntt.co.jp>
    Signed-off-by: Joerg Roedel <joerg.roedel@....com>

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index ae38b24..09261dc 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -1360,6 +1360,9 @@ static void *alloc_coherent(struct device *dev, size_t size,
 	if (!check_device(dev))
 		return NULL;
 
+	if (!get_device_resources(dev, &iommu, &domain, &devid))
+		flag &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
+
 	virt_addr = (void *)__get_free_pages(flag, get_order(size));
 	if (!virt_addr)
 		return 0;
@@ -1367,8 +1370,6 @@ 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;

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