On Thu, Sep 29, 2022 at 05:33:01PM +0200, Niklas Schnelle wrote: > The domain->geometry.aperture_end specifies the last valid address treat > it as such when checking if a DMA address is valid. > > Reviewed-by: Pierre Morel <pmorel@xxxxxxxxxxxxx> > Reviewed-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx> > Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx> > --- > drivers/iommu/s390-iommu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c > index ed0e64f478cf..6d4a9c7db32c 100644 > --- a/drivers/iommu/s390-iommu.c > +++ b/drivers/iommu/s390-iommu.c > @@ -210,7 +210,7 @@ static int s390_iommu_update_trans(struct s390_domain *s390_domain, > int rc = 0; > > if (dma_addr < s390_domain->domain.geometry.aperture_start || > - dma_addr + size > s390_domain->domain.geometry.aperture_end) > + dma_addr + size > s390_domain->domain.geometry.aperture_end + 1) The reason the iommu layer uses 'last' (= start + size - 1) not 'end' is to allow for the very last byte of the range to be used. Meaning (start + size) == 0 in some cases due to the overflow. Generally when working with lasts's I prefer people write code in a way that doesn't trigger the overflow, because there are some complicated C rules about integer promotion that can mean the desired overflow silently doesn't happen in obscure cases - especially if unsigned long != u64 So, I'd write this as: (dma_addr + size - 1) > s390_domain->domain.geometry.aperture_end Jason
