Re: [PATCH 08/16] sparc64: define untagged_addr()

[Khalid Aziz <khalid.aziz@oracle.com>]

On 6/11/19 8:40 AM, Christoph Hellwig wrote:
> Add a helper to untag a user pointer.  This is needed for ADI support
> in get_user_pages_fast.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/sparc/include/asm/pgtable_64.h | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)

Looks good to me.

Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>

> 
> diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
> index f0dcf991d27f..1904782dcd39 100644
> --- a/arch/sparc/include/asm/pgtable_64.h
> +++ b/arch/sparc/include/asm/pgtable_64.h
> @@ -1076,6 +1076,28 @@ static inline int io_remap_pfn_range(struct vm_area_struct *vma,
>  }
>  #define io_remap_pfn_range io_remap_pfn_range 
>  
> +static inline unsigned long untagged_addr(unsigned long start)
> +{
> +	if (adi_capable()) {
> +		long addr = start;
> +
> +		/* If userspace has passed a versioned address, kernel
> +		 * will not find it in the VMAs since it does not store
> +		 * the version tags in the list of VMAs. Storing version
> +		 * tags in list of VMAs is impractical since they can be
> +		 * changed any time from userspace without dropping into
> +		 * kernel. Any address search in VMAs will be done with
> +		 * non-versioned addresses. Ensure the ADI version bits
> +		 * are dropped here by sign extending the last bit before
> +		 * ADI bits. IOMMU does not implement version tags.
> +		 */
> +		return (addr << (long)adi_nbits()) >> (long)adi_nbits();
> +	}
> +
> +	return start;
> +}
> +#define untagged_addr untagged_addr
> +
>  #include <asm/tlbflush.h>
>  #include <asm-generic/pgtable.h>
>  
>