Re: [PATCH v4 06/33] crypto: rockchip: add fallback for cipher

LABBE Corentin
2022-04-11T08:42:39Z

Le Mon, Apr 04, 2022 at 12:26:15PM +0100, John Keeping a écrit :
> On Fri, Apr 01, 2022 at 08:17:37PM +0000, Corentin Labbe wrote:
> > The hardware does not handle 0 size length request, let's add a
> > fallback.
> > Furthermore fallback will be used for all unaligned case the hardware
> > cannot handle.
> >
> > Fixes: ce0183cb6464b ("crypto: rockchip - switch to skcipher API")
> > Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
> > ---
> > diff --git a/drivers/crypto/rockchip/rk3288_crypto_skcipher.c b/drivers/crypto/rockchip/rk3288_crypto_skcipher.c
> > index bbd0bf52bf07..c6b601086c04 100644
> > --- a/drivers/crypto/rockchip/rk3288_crypto_skcipher.c
> > +++ b/drivers/crypto/rockchip/rk3288_crypto_skcipher.c
> > @@ -13,6 +13,71 @@
> >
> > #define RK_CRYPTO_DEC BIT(0)
> >
> > +static int rk_cipher_need_fallback(struct skcipher_request *req)
> > +{
> > + struct scatterlist *sgs, *sgd;
> > + unsigned int todo, len;
> > + unsigned int bs = crypto_skcipher_blocksize(tfm);
> > +
> > + if (!req->cryptlen)
> > + return true;
> > +
> > + len = req->cryptlen;
> > + sgs = req->src;
> > + while (sgs) {
> > + if (!IS_ALIGNED(sgs->offset, sizeof(u32))) {
> > + return true;
> > + }
> > + todo = min(len, sgs->length);
> > + if (todo % bs) {
> > + return true;
> > + }
> > + len -= todo;
> > + sgs = sg_next(sgs);
> > + }
> > + len = req->cryptlen;
> > + sgd = req->dst;
> > + while (sgd) {
> > + if (!IS_ALIGNED(sgd->offset, sizeof(u32))) {
> > + return true;
> > + }
> > + todo = min(len, sgd->length);
> > + if (todo % bs) {
> > + return true;
> > + }
> > + len -= todo;
> > + sgd = sg_next(sgd);
> > + }
> > + sgs = req->src;
> > + sgd = req->dst;
> > + while (sgs && sgd) {
> > + if (sgs->length != sgd->length)
>
> This check still seems to be triggering the fallback when it is not
> needed.
>
> I've done some testing with fscrypt and the series is working great, but
> the stats show the fallback triggering more than I'd expect. With some
> extra logging here I see output like:
>
> sgs->length=32 sgd->length=255 req->cryptlen=16
>
> In this case sgs and sgd are both the first (and only) entries in the
> list. Should this take account of req->cryptlen as well?
>
> In fact, can't this whole function be folded into one loop over src and
> dst at the same time, since all the checks must be the same? Something
> like this (untested):
>
> while (sgs && sgd) {
> if (!IS_ALIGNED(sgs->offset, sizeof(u32)) ||
> !IS_ALIGNED(sgd->offset, sizeof(u32)))
> return true;
>
> todo = min(len, sgs->length);
> if (todo % bs)
> return true;
>
> if (sgd->length < todo)
> return true;
>
> len -= todo;
> sgs = sg_next(sgs);
> sgd = sg_next(sgd);
> }
>
> if (len)
> return true;
>

Thanks, for this hint, I will use it.

Regards