Re: [PATCH] crypto: gcm - fix cacheline sharing

[Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>]

On Thu, 30 May 2019 at 15:45, Iuliana Prodan <iuliana.prodan@xxxxxxx> wrote:
>
> On 5/30/2019 4:34 PM, Herbert Xu wrote:
> > On Thu, May 30, 2019 at 01:29:41PM +0000, Iuliana Prodan wrote:
> >>
> >> I've tried coping the IV before the extended descriptor allocation, but
> >> is not working and to make it work will need to make more changes in
> >> CAAM. We need the original iv, and if we move it before
> >> skcipher_edesc_alloc we lose it.
> >> The fix exclusively in CAAM drv, to copy iv before DMA map, is more complex.
> >
> > Why doesn't it work (apart from the fact that this only makes sense
> > for CBC and yet you're doing it for everything including CTR)?
> >
> > Cheers,
> >
>
> On the current structure of caamalg, to work, iv needs to be copied
> before memcpy(iv, req->iv, ivsize), from skcipher_edesc_alloc function.
> For this we need edesc, but this cannot be allocated before knowing how
> much memory we need. So, to make it work, we'll need to modify more in CAAM.
>

Would this work?

diff --git a/drivers/crypto/caam/caamalg.c b/drivers/crypto/caam/caamalg.c
index c0ece44f303b..2ef2f76a3cb8 100644
--- a/drivers/crypto/caam/caamalg.c
+++ b/drivers/crypto/caam/caamalg.c
@@ -1832,22 +1832,25 @@ static int skcipher_decrypt(struct
skcipher_request *req)
        struct caam_ctx *ctx = crypto_skcipher_ctx(skcipher);
        int ivsize = crypto_skcipher_ivsize(skcipher);
        struct device *jrdev = ctx->jrdev;
+       u8 out_iv[AES_BLOCK_SIZE];
        u32 *desc;
        int ret = 0;

-       /* allocate extended descriptor */
-       edesc = skcipher_edesc_alloc(req, DESC_JOB_IO_LEN * CAAM_CMD_SZ);
-       if (IS_ERR(edesc))
-               return PTR_ERR(edesc);
-
        /*
         * The crypto API expects us to set the IV (req->iv) to the last
         * ciphertext block.
         */
        if (ivsize)
-               scatterwalk_map_and_copy(req->iv, req->src, req->cryptlen -
+               scatterwalk_map_and_copy(out_iv, req->src, req->cryptlen -
                                         ivsize, ivsize, 0);

+       /* allocate extended descriptor */
+       edesc = skcipher_edesc_alloc(req, DESC_JOB_IO_LEN * CAAM_CMD_SZ);
+       if (IS_ERR(edesc))
+               return PTR_ERR(edesc);
+
+       memcpy(req->iv, out_iv, ivsize);
+
        /* Create and submit job descriptor*/
        init_skcipher_job(req, edesc, false);
        desc = edesc->hw_desc;