On 12/6/2016 4:24 AM, Alex Williamson wrote:
> On Tue, 6 Dec 2016 02:38:01 +0530
> Kirti Wankhede <kwankh...@nvidia.com> wrote:
>
>> In the functions of pin_pages/unpin_pages from mdev vendor driver,
>> vfio_find_dma() should be called with size as PAGE_SIZE instead of 0.
>> vfio_find_dma() searches for the range in dma_list.
>>
>> In vfio_dma_do_unmap(), vfio_find_dma() when used to look for start
>> address of unmap->iova, size should be 1, not 0. Otherwise vfio_find_dma()
>> returns NULL.
>
> Hi Kirti,
>
> I'd prefer to fix the preexisting case of this issue as a separate
> patch, we might want to backport it for stable trees separately from the
> new cases introduced with mdev. It would also be great if we could go
> into some detail about why size=0 doesn't work in these cases, ie.
> vfio_find_dma() accounting for the end address of the range makes it
> fall through at the wrong branch point. For the case of the
> preexisting issue, it would also be useful to mention that the other
> case of passing size=0 works correctly due to the -1 in the start
> address calculation. Finally, I think I agree with your choice to use
> PAGE_SIZE in one case and 1 in the preexisting case, but perhaps we
> could spell that out as one is related to a page size interface and the
> other is trying to test boundary conditions. Thanks,
>
Thanks Alex,
Actual problem here is: vfio_dma keeps track of address range from
(dma->iova + 0) to (dma->iova + dma->size - 1), while vfio_find_dma()
search logic looks for range from (dma->iova + 1) to (dma->iova +
dma->size). So either we have to fix the size argument send to
vfio_find_dma() or we have to fix rb-tree creation and search logic.
I took the former path here. I'll add this detail in commit description
and split it as you mentioned above.
Thanks,
Kirti
> Alex
>
>> Signed-off-by: Kirti Wankhede <kwankh...@nvidia.com>
>> Signed-off-by: Neo Jia <c...@nvidia.com>
>> Change-Id: Iee6fd45441c342b5e8626087046b2e0075d19a08
>> ---
>> drivers/vfio/vfio_iommu_type1.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c
>> b/drivers/vfio/vfio_iommu_type1.c
>> index a28fbddb505c..023fba7b8d5a 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -581,7 +581,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>> struct vfio_pfn *vpfn;
>>
>> iova = user_pfn[i] << PAGE_SHIFT;
>> - dma = vfio_find_dma(iommu, iova, 0);
>> + dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
>> if (!dma) {
>> ret = -EINVAL;
>> goto pin_unwind;
>> @@ -622,7 +622,7 @@ pin_unwind:
>> dma_addr_t iova;
>>
>> iova = user_pfn[j] << PAGE_SHIFT;
>> - dma = vfio_find_dma(iommu, iova, 0);
>> + dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
>> vfio_unpin_page_external(dma, iova, do_accounting);
>> phys_pfn[j] = 0;
>> }
>> @@ -659,7 +659,7 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
>> dma_addr_t iova;
>>
>> iova = user_pfn[i] << PAGE_SHIFT;
>> - dma = vfio_find_dma(iommu, iova, 0);
>> + dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
>> if (!dma)
>> goto unpin_exit;
>> vfio_unpin_page_external(dma, iova, do_accounting);
>> @@ -826,7 +826,7 @@ again:
>> * mappings within the range.
>> */
>> if (iommu->v2) {
>> - dma = vfio_find_dma(iommu, unmap->iova, 0);
>> + dma = vfio_find_dma(iommu, unmap->iova, 1);
>> if (dma && dma->iova != unmap->iova) {
>> ret = -EINVAL;
>> goto unlock;
>
