Messages in this thread | | | Date | Wed, 06 Aug 2008 08:29:49 -0400 | From | Prarit Bhargava <> | Subject | Re: [PATCH]: PCI: GART iommu alignment fixes [v2] |
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FUJITA Tomonori wrote: > On Mon, 28 Jul 2008 15:23:35 -0700 > Jesse Barnes <jbarnes@virtuousgeek.org> wrote: > > >> On Wednesday, July 23, 2008 4:14 pm FUJITA Tomonori wrote: >> >>> On Thu, 24 Jul 2008 00:10:33 +0200 >>> >>> Joerg Roedel <joro@8bytes.org> wrote: >>> >>>> On Wed, Jul 23, 2008 at 07:19:43AM -0400, Prarit Bhargava wrote: >>>> >>>>> pci_alloc_consistent/dma_alloc_coherent does not return size aligned >>>>> addresses. >>>>> >>>>> >From Documentation/DMA-mapping.txt: >>>>> >>>>> "pci_alloc_consistent returns two values: the virtual address which you >>>>> can use to access it from the CPU and dma_handle which you pass to the >>>>> card. >>>>> >>>>> The cpu return address and the DMA bus master address are both >>>>> guaranteed to be aligned to the smallest PAGE_SIZE order which >>>>> is greater than or equal to the requested size. This invariant >>>>> exists (for example) to guarantee that if you allocate a chunk >>>>> which is smaller than or equal to 64 kilobytes, the extent of the >>>>> buffer you receive will not cross a 64K boundary." >>>>> >>>> Interesting. Have you experienced any problems because of that >>>> misbehavior in the GART code? AMD IOMMU currently also violates this >>>> requirement. I will send a patch to fix that there too. >>>> >>> IIRC, only PARISC and POWER IOMMUs follow the above rule. So I also >>> wondered what problem he hit. >>> >> Prarit, what's the latest here? The v3 patch I have from you doesn't apply to >> my tree but it looks like a good fix. Care to send me a new patch against my >> for-linus branch? >> > > I'm not sure how the following cast to 'unsigned long long' fixes > something on X86_64. > >
You can write a very simple module that kmalloc's a pci_dev, sets up some trivial values for the dev, and then calls pci_alloc_consistent. You will panic 100% of the time because 'dma_get_seg_boundary(dev) + 1' overflows an unsigned long.
>> Signed-off-by: Prarit Bhargava <prarit@redhat.com> >> >> diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c >> index 744126e..d3eb527 100644 >> --- a/arch/x86/kernel/pci-gart_64.c >> +++ b/arch/x86/kernel/pci-gart_64.c >> @@ -85,7 +85,8 @@ AGPEXTERN __u32 *agp_gatt_table; >> static unsigned long next_bit; /* protected by iommu_bitmap_lock */ >> static int need_flush; /* global flush state. set for each gart wrap */ >> >> -static unsigned long alloc_iommu(struct device *dev, int size) >> +static unsigned long alloc_iommu(struct device *dev, int size, >> + unsigned long mask) >> { >> unsigned long offset, flags; >> unsigned long boundary_size; >> @@ -93,16 +94,17 @@ static unsigned long alloc_iommu(struct device *dev, int size) >> >> base_index = ALIGN(iommu_bus_base & dma_get_seg_boundary(dev), >> PAGE_SIZE) >> PAGE_SHIFT; >> - boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1, >> + boundary_size = ALIGN((unsigned long long)dma_get_seg_boundary(dev) + 1, >> PAGE_SIZE) >> PAGE_SHIFT; >> > > I don't think that the following code works since the size is not > always a power of 2. >
> > >> @@ -265,7 +268,7 @@ static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem, >> static dma_addr_t >> gart_map_simple(struct device *dev, phys_addr_t paddr, size_t size, int dir) >> { >> - dma_addr_t map = dma_map_area(dev, paddr, size, dir); >> + dma_addr_t map = dma_map_area(dev, paddr, size, dir, size - 1); >>
Maybe I'm missing something -- what implies size has to be a power of two?
P.
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