On Wed, 2020-12-16 at 12:10 +0000, Robin Murphy wrote:
> On 2020-12-16 10:36, Yong Wu wrote:
> > Currently gather->end is "unsigned long" which may be overflow in
> > arch32 in the corner case: 0xfff00000 + 0x100000(iova + size).
> > Although it doesn't affect the size(end - start), it affects the checking
> > "gather->end < end"
>
> This won't help the same situation at the top of a 64-bit address space,
> though, and now that we have TTBR1 support for AArch64 format that is
> definitely a thing. Better to just encode the end address as the actual
> end address, i.e. iova + size - 1. We don't lose anything other than the
> ability to encode zero-sized invalidations that don't make sense anyway.
Thanks for the suggestion. "iova + size - 1" is better. Also I will
change the "size" to "gather->end - gather->start + 1" in the iotlb_sync
of arm-smmu-v3.c and mtk_iommu.c.
>
> Robin.
>
> > Fixes: a7d20dc19d9e ("iommu: Introduce struct iommu_iotlb_gather for
> > batching TLB flushes")
> > Signed-off-by: Yong Wu <yong...@mediatek.com>
> > ---
> > include/linux/iommu.h | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index 794d4085edd3..6e907a95d981 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -178,7 +178,7 @@ enum iommu_dev_features {
> > */
> > struct iommu_iotlb_gather {
> > unsigned long start;
> > - unsigned long end;
> > + unsigned long long end;
> > size_t pgsize;
> > };
> >
> > @@ -537,7 +537,8 @@ static inline void iommu_iotlb_gather_add_page(struct
> > iommu_domain *domain,
> > struct iommu_iotlb_gather
> > *gather,
> > unsigned long iova, size_t size)
> > {
> > - unsigned long start = iova, end = start + size;
> > + unsigned long start = iova;
> > + unsigned long long end = start + size;
> >
> > /*
> > * If the new page is disjoint from the current range or is mapped at
> >
