Messages in this thread | | | Subject | Re: [PATCH] iommu/dma: Fix IOVA reserve dma ranges | From | Robin Murphy <> | Date | Wed, 9 Sep 2020 13:05:49 +0100 |
| |
On 2020-09-09 06:32, Srinath Mannam wrote: > Fix IOVA reserve failure for memory regions listed in dma-ranges in the > following cases. > > - start address of memory region is 0x0.
That's fair enough, and in fact generalises to the case of zero-sized gaps between regions, which is indeed an oversight.
> - end address of a memory region is equal to start address of next memory > region.
This part doesn't make much sense, however - if the regions described in bridge->dma_ranges overlap, that's a bug in whoever created a malformed list to begin with. Possibly it's just poor wording, and you're using "memory regions" to refer to any or all of the dma_ranges, the reserved IOVA ranges, and what "start" and "end" in this function represent which isn't quite either of those.
> Fixes: aadad097cd46f ("iommu/dma: Reserve IOVA for PCIe inaccessible DMA address") > Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com> > --- > drivers/iommu/dma-iommu.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 5141d49a046b..0a3f67a4f9ae 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -213,14 +213,21 @@ static int iova_reserve_pci_windows(struct pci_dev *dev, > resource_list_for_each_entry(window, &bridge->dma_ranges) { > end = window->res->start - window->offset; > resv_iova: > + if (end < start) { > + /* dma_ranges list should be sorted */ > + dev_err(&dev->dev, "Failed to reserve IOVA\n"); > + return -EINVAL; > + } > + /* > + * Skip the cases when start address of first memory region is > + * 0x0 and end address of one memory region and start address > + * of next memory region are equal. Reserve IOVA for rest of > + * addresses fall in between given memory ranges. > + */ > if (end > start) { > lo = iova_pfn(iovad, start); > hi = iova_pfn(iovad, end); > reserve_iova(iovad, lo, hi); > - } else {
Surely this only needs to be a one-liner?
- } else { + } else if (end < start) {
(or possibly "end != start"; I can't quite decide which expresses the semantic intent better)
The rest just looks like unnecessary churn - I don't think it needs commenting that a sorted list may simply not have gaps between entries, and as above I think the wording of that comment is actively misleading.
Robin.
> - /* dma_ranges list should be sorted */ > - dev_err(&dev->dev, "Failed to reserve IOVA\n"); > - return -EINVAL; > } > > start = window->res->end - window->offset + 1; >
| |