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    SubjectRe: [PATCH] ipr: don't doublefree pages from scatterlist
    Date
    On Monday 06 February 2006 17:45, Hugh Dickins wrote:

    >
    > But all this presupposes that someone is suddenly going to change the
    > x86_64 gart_map_sg (and subfunctions), or else force its iommu=nomerge:
    > that won't be me.

    Ok i changed it to conform to the gospel. I gave it some basic pounding LTP/dd IO with
    and without IOMMU force, but it's not that well tested. More testing welcome.

    -Andi

    Don't touch the non DMA members in the sg list in dma_map_sg in the IOMMU

    Some drivers (in particular ipr) ran into problems because they
    reused the sg lists after passing them to pci_map_sg(). The merging
    procedure in the K8 GART IOMMU corrupted the state. This patch
    changes it to only touch the dma* entries during merging,
    but not the other fields. Approach suggested by Dave Miller.

    I did some basic tests with CONFIG_IOMMU_DEBUG (LTP, large dd)
    and without and it hold up, but needs more testing.

    Signed-off-by: Andi Kleen <ak@suse.de>

    Index: linux/arch/x86_64/kernel/pci-gart.c
    ===================================================================
    --- linux.orig/arch/x86_64/kernel/pci-gart.c
    +++ linux/arch/x86_64/kernel/pci-gart.c
    @@ -300,7 +300,7 @@ void gart_unmap_sg(struct device *dev, s

    for (i = 0; i < nents; i++) {
    struct scatterlist *s = &sg[i];
    - if (!s->dma_length || !s->length)
    + if (!s->dma_length)
    break;
    dma_unmap_single(dev, s->dma_address, s->dma_length, dir);
    }
    @@ -354,7 +354,6 @@ static int __dma_map_cont(struct scatter

    BUG_ON(i > start && s->offset);
    if (i == start) {
    - *sout = *s;
    sout->dma_address = iommu_bus_base;
    sout->dma_address += iommu_page*PAGE_SIZE + s->offset;
    sout->dma_length = s->length;
    @@ -369,7 +368,7 @@ static int __dma_map_cont(struct scatter
    SET_LEAK(iommu_page);
    addr += PAGE_SIZE;
    iommu_page++;
    - }
    + }
    }
    BUG_ON(iommu_page - iommu_start != pages);
    return 0;
    @@ -381,7 +380,6 @@ static inline int dma_map_cont(struct sc
    {
    if (!need) {
    BUG_ON(stopat - start != 1);
    - *sout = sg[start];
    sout->dma_length = sg[start].length;
    return 0;
    }
    -
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