Messages in this thread | | | Subject | Re: [PATCH 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range | From | Robin Murphy <> | Date | Mon, 26 Nov 2018 13:18:53 +0000 |
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On 26/11/2018 06:44, Souptick Joarder wrote: > On Sat, Nov 24, 2018 at 3:04 AM Matthew Wilcox <willy@infradead.org> wrote: >> >> On Fri, Nov 23, 2018 at 05:23:06PM +0000, Robin Murphy wrote: >>> On 15/11/2018 15:49, Souptick Joarder wrote: >>>> Convert to use vm_insert_range() to map range of kernel >>>> memory to user vma. >>>> >>>> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com> >>>> Reviewed-by: Matthew Wilcox <willy@infradead.org> >>>> --- >>>> drivers/iommu/dma-iommu.c | 12 ++---------- >>>> 1 file changed, 2 insertions(+), 10 deletions(-) >>>> >>>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >>>> index d1b0475..69c66b1 100644 >>>> --- a/drivers/iommu/dma-iommu.c >>>> +++ b/drivers/iommu/dma-iommu.c >>>> @@ -622,17 +622,9 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp, >>>> int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma) >>>> { >>>> - unsigned long uaddr = vma->vm_start; >>>> - unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT; >>>> - int ret = -ENXIO; >>>> + unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT; >>>> - for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) { >>>> - ret = vm_insert_page(vma, uaddr, pages[i]); >>>> - if (ret) >>>> - break; >>>> - uaddr += PAGE_SIZE; >>>> - } >>>> - return ret; >>>> + return vm_insert_range(vma, vma->vm_start, pages, count); >>> >>> AFIACS, vm_insert_range() doesn't respect vma->vm_pgoff, so doesn't this >>> break partial mmap()s of a large buffer? (which I believe can be a thing) >> >> Whoops. That should have been: >> >> return vm_insert_range(vma, vma->vm_start, pages + vma->vm_pgoff, count); > > I am unable to trace back where vma->vm_pgoff is set for this driver ? if any ?
This isn't a driver - it's a DMA API backend, so any caller of dma_mmap_*() could potentially end up here (similarly for patch 2/9).
Robin.
> If default value set to 0 then I think existing code is correct. > >> >> I suppose. >> > >> Although arguably we should respect vm_pgoff inside vm_insert_region() >> and then callers automatically get support for vm_pgoff without having >> to think about it ... > > I assume, vm_insert_region() means vm_insert_range(). If we respect vm_pgoff > inside vm_insert_range, for any uninitialized/ error value set for vm_pgoff from > drivers will introduce a bug inside core mm which might be difficult > to trace back. > But when vm_pgoff set and passed from caller (drivers) it might be > easy to figure out. > >> although we should then also pass in the length >> of the pages array to avoid pages being mapped in which aren't part of >> the allocated array. > > Mostly Partial mapping is done by starting from an index and mapped it till > end of pages array. Calculating length of the pages array will have a small > overhead for each drivers. > > Please correct me if I am wrong. >
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