On Wed, Mar 20, 2019 at 03:51:30PM +0100, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
>
> mlx4_get_umem_mr() uses provided user pointers for vma lookups, which can
> only by done with untagged pointers.
>
> Untag user pointers in this function.
>
> Signed-off-by: Andrey Konovalov
> ---
> drivers/infiniband/hw/mlx4/mr.c | 7 ---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/hw/mlx4/mr.c b/drivers/infiniband/hw/mlx4/mr.c
> index 395379a480cb..9a35ed2c6a6f 100644
> --- a/drivers/infiniband/hw/mlx4/mr.c
> +++ b/drivers/infiniband/hw/mlx4/mr.c
> @@ -378,6 +378,7 @@ static struct ib_umem *mlx4_get_umem_mr(struct ib_udata
> *udata, u64 start,
>* again
>*/
> if (!ib_access_writable(access_flags)) {
> + unsigned long untagged_start = untagged_addr(start);
> struct vm_area_struct *vma;
>
> down_read(>mm->mmap_sem);
> @@ -386,9 +387,9 @@ static struct ib_umem *mlx4_get_umem_mr(struct ib_udata
> *udata, u64 start,
>* cover the memory, but for now it requires a single vma to
>* entirely cover the MR to support RO mappings.
>*/
> - vma = find_vma(current->mm, start);
> - if (vma && vma->vm_end >= start + length &&
> - vma->vm_start <= start) {
> + vma = find_vma(current->mm, untagged_start);
> + if (vma && vma->vm_end >= untagged_start + length &&
> + vma->vm_start <= untagged_start) {
> if (vma->vm_flags & VM_WRITE)
> access_flags |= IB_ACCESS_LOCAL_WRITE;
> } else {
> --
Thanks,
Reviewed-by: Leon Romanovsky
Interesting, the followup question is why mlx4 is only one driver in IB which
needs such code in umem_mr. I'll take a look on it.
Thanks
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