Re: [Xen-devel] [PATCH v8 for-4.9 3/5] hvm/dmop: Implement copy_{to, from}_guest_buf() in terms of raw accessors

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: jennifer.herbert@xxxxxxxxxx [mailto:jennifer.herbert@xxxxxxxxxx]
> Sent: 21 April 2017 15:06
> To: Xen-devel <xen-devel@xxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Jennifer Herbert
> <jennifer.herbert@xxxxxxxxxx>; Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Jan
> Beulich <JBeulich@xxxxxxxx>; Julien Grall <julien.grall@xxxxxxx>
> Subject: [PATCH v8 for-4.9 3/5] hvm/dmop: Implement copy_{to,
> from}_guest_buf() in terms of raw accessors
> 
> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
> This also allows the usual cases to be simplified, by omitting an unnecessary
> buf parameters, and because the macros can appropriately size the object.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Jennifer Herbert <Jennifer.Herbert@xxxxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> --
> CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
> CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> ---
> Rebased.
> ---
>  xen/arch/x86/hvm/dm.c | 43 ++++++++++++++++++++++++++---------------
> --
>  1 file changed, 26 insertions(+), 17 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
> index 89186d2..b31c252 100644
> --- a/xen/arch/x86/hvm/dm.c
> +++ b/xen/arch/x86/hvm/dm.c
> @@ -32,38 +32,47 @@ struct dmop_args {
>      struct xen_dm_op_buf buf[2];
>  };
> 
> -static bool copy_buf_from_guest(const xen_dm_op_buf_t bufs[],
> -                                unsigned int nr_bufs, void *dst,
> -                                unsigned int idx, size_t dst_size)
> +static bool _raw_copy_from_guest_buf(void *dst,
> +                                     const struct dmop_args *args,
> +                                     unsigned int buf_idx,
> +                                     size_t dst_bytes)
>  {
>      size_t buf_bytes;
> 
> -    if ( idx >= nr_bufs )
> +    if ( buf_idx >= args->nr_bufs )
>          return false;
> 
> -    buf_bytes = bufs[idx].size;
> -    if ( dst_size > buf_bytes )
> +    buf_bytes =  args->buf[buf_idx].size;
> +
> +    if ( dst_bytes > buf_bytes )
>          return false;
> 
> -    return !copy_from_guest(dst, bufs[idx].h, dst_size);
> +    return !copy_from_guest(dst, args->buf[buf_idx].h, dst_bytes);
>  }
> 
> -static bool copy_buf_to_guest(const xen_dm_op_buf_t bufs[],
> -                              unsigned int nr_bufs, unsigned int idx,
> -                              const void *src, size_t src_size)
> +static bool _raw_copy_to_guest_buf(const struct dmop_args *args,
> +                                   unsigned int buf_idx,
> +                                   const void *src, size_t src_bytes)
>  {
>      size_t buf_bytes;
> 
> -    if ( idx >= nr_bufs )
> +    if ( buf_idx >= args->nr_bufs )
>          return false;
> 
> -    buf_bytes = bufs[idx].size;
> -    if ( src_size > buf_bytes )
> +    buf_bytes = args->buf[buf_idx].size;
> +
> +    if ( src_bytes > buf_bytes )
>          return false;
> 
> -    return !copy_to_guest(bufs[idx].h, src, src_size);
> +    return !copy_to_guest(args->buf[buf_idx].h, src, src_bytes);
>  }
> 
> +#define COPY_FROM_GUEST_BUF(dst, args, buf_idx) \
> +    _raw_copy_from_guest_buf(&dst, args, buf_idx, sizeof(dst))
> +
> +#define COPY_TO_GUEST_BUF(args, buf_idx, src) \
> +    _raw_copy_to_guest_buf(args, buf_idx, &src, sizeof(src))
> +
>  static int track_dirty_vram(struct domain *d, xen_pfn_t first_pfn,
>                              unsigned int nr, const struct xen_dm_op_buf *buf)
>  {
> @@ -314,7 +323,7 @@ static int dm_op(const struct dmop_args *op_args)
>      if ( rc )
>          goto out;
> 
> -    if ( !copy_buf_from_guest(&op_args->buf[0], op_args->nr_bufs, &op, 0,
> sizeof(op)) )
> +    if ( !COPY_FROM_GUEST_BUF(op, op_args, 0) );
>      {
>          rc = -EFAULT;
>          goto out;
> @@ -570,8 +579,8 @@ static int dm_op(const struct dmop_args *op_args)
>      }
> 
>      if ( (!rc || rc == -ERESTART) &&
> -         !const_op &&
> -         !copy_buf_to_guest(&op_args->buf[0], op_args->nr_bufs, 0, &op,
> sizeof(op)) )
> +         !const_op && !COPY_TO_GUEST_BUF(op_args, 0, op) )
> +
>          rc = -EFAULT;
> 
>   out:
> --
> 2.1.4


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