Re: [PATCH v3 08/24] iommu/io-pgtable-arm-v7s: Use ias to check the valid iova in unmap

Will Deacon
2020-10-23T11:18:04Z

On Wed, Sep 30, 2020 at 03:06:31PM +0800, Yong Wu wrote:
> Use the ias for the valid iova checking in arm_v7s_unmap. This is a
> preparing patch for supporting iova 34bit for MediaTek.
> BTW, change the ias/oas checking format in arm_v7s_map.
>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
> drivers/iommu/io-pgtable-arm-v7s.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index a688f22cbe3b..4c9d8dccfc5a 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -526,8 +526,7 @@ static int arm_v7s_map(struct io_pgtable_ops *ops, unsigned long iova,
> if (!(prot & (IOMMU_READ | IOMMU_WRITE)))
> return 0;
>
> - if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias) ||
> - paddr >= (1ULL << data->iop.cfg.oas)))
> + if (WARN_ON(iova >> data->iop.cfg.ias || paddr >> data->iop.cfg.oas))
> return -ERANGE;

As discussed when reviewing these for Android, please leave this code as-is.

>
> ret = __arm_v7s_map(data, iova, paddr, size, prot, 1, data->pgd, gfp);
> @@ -717,7 +716,7 @@ static size_t arm_v7s_unmap(struct io_pgtable_ops *ops, unsigned long iova,
> {
> struct arm_v7s_io_pgtable *data = io_pgtable_ops_to_data(ops);
>
> - if (WARN_ON(upper_32_bits(iova)))
> + if (WARN_ON(iova >> data->iop.cfg.ias))
> return 0;

And avoid the UB here for 32-bit machines by comparing with 1ULL <<
iop.cfg.ias instead.

Thanks,

Will