Re: [PATCH] x86: fix nommu_alloc_coherent allocation with NULL device argument

Joerg Roedel
2008-09-05T11:57:19Z

Andi,

I guess you made the dma_mask of the fallback_dev 32 bit a long time
ago. Is there any reason it cannot be 24 bit?

Joerg

On Fri, Sep 05, 2008 at 12:40:49PM +0200, Joerg Roedel wrote:
> I agree with this patch in principle. It fixes the problem. But I think
> we should evaluate if we can change the dma_mask of the fallback_dev to
> 24 bit.
>
> On Fri, Sep 05, 2008 at 05:58:47PM +0900, FUJITA Tomonori wrote:
> > We need to use __GFP_DMA for NULL device argument (fallback_dev) with
> > pci-nommu. It's a hack for ISA (and some old code) so we need to use
> > GFP_DMA.
> >
> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > ---
> > arch/x86/kernel/pci-nommu.c | 5 +----
> > include/asm-x86/dma-mapping.h | 2 ++
> > 2 files changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/kernel/pci-nommu.c b/arch/x86/kernel/pci-nommu.c
> > index 73853d3..526b2db 100644
> > --- a/arch/x86/kernel/pci-nommu.c
> > +++ b/arch/x86/kernel/pci-nommu.c
> > @@ -83,7 +83,6 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
> > if (hwdev->dma_mask == NULL)
> > return NULL;
> >
> > - gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
> > gfp |= __GFP_ZERO;
> >
> > dma_mask = hwdev->coherent_dma_mask;
> > @@ -96,14 +95,12 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
> > node = dev_to_node(hwdev);
> >
> > #ifdef CONFIG_X86_64
> > - if (dma_mask <= DMA_32BIT_MASK)
> > + if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
> > gfp |= GFP_DMA32;
> > #endif
> > -
> > /* No alloc-free penalty for ISA devices */
> > if (dma_mask == DMA_24BIT_MASK)
> > gfp |= GFP_DMA;
> > -
>
> Please leave these spare lines where they are. They increase the
> readability of the code imho.
>
> > again:
> > page = alloc_pages_node(node, gfp, get_order(size));
> > if (!page)
> > diff --git a/include/asm-x86/dma-mapping.h b/include/asm-x86/dma-mapping.h
> > index 3a9a6f5..de4495e 100644
> > --- a/include/asm-x86/dma-mapping.h
> > +++ b/include/asm-x86/dma-mapping.h
> > @@ -246,6 +246,8 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
> > struct dma_mapping_ops *ops = get_dma_ops(dev);
> > void *memory;
> >
> > + gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
> > +
> > if (dma_alloc_from_coherent(dev, size, dma_handle, &memory))
> > return memory;
> >
> > --
> > 1.5.4.2
> >
> >
>
> --
> | AMD Saxony Limited Liability Company & Co. KG
> Operating | Wilschdorfer Landstr. 101, 01109 Dresden, Germany
> System | Register Court Dresden: HRA 4896
> Research | General Partner authorized to represent:
> Center | AMD Saxony LLC (Wilmington, Delaware, US)
> | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy
>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/iommu
>

--
| AMD Saxony Limited Liability Company & Co. KG
Operating | Wilschdorfer Landstr. 101, 01109 Dresden, Germany
System | Register Court Dresden: HRA 4896
Research | General Partner authorized to represent:
Center | AMD Saxony LLC (Wilmington, Delaware, US)
| General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy