With the recent kmap change, some tests which were conditional on
CONFIG_DEBUG_HIGHMEM now are enabled by default.
This permit to detect a problem in sun4i-ss usage of kmap.

sun4i-ss uses two kmap via sg_miter (one for input, one for output), but
using two kmap at the same time is hard:
"the ordering has to be correct and with sg_miter that's probably hard to get
right." (quoting Tlgx)

So the easiest solution is to never have two sg_miter/kmap open at the same 
time.
After each use of sg_miter, I store the current index, for being able to
resume sg_miter to the right place.

Fixes: 6298e948215f ("crypto: sunxi-ss - Add Allwinner Security System crypto 
accelerator")
Signed-off-by: Corentin Labbe <cla...@baylibre.com>
---
 .../allwinner/sun4i-ss/sun4i-ss-cipher.c      | 109 +++++++++++-------
 1 file changed, 65 insertions(+), 44 deletions(-)

diff --git a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c 
b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c
index 5759fa79f293..ffa628c89e21 100644
--- a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c
+++ b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c
@@ -31,6 +31,8 @@ static int noinline_for_stack sun4i_ss_opti_poll(struct 
skcipher_request *areq)
        unsigned int ileft = areq->cryptlen;
        unsigned int oleft = areq->cryptlen;
        unsigned int todo;
+       unsigned long pi = 0, po = 0; /* progress for in and out */
+       bool miter_err;
        struct sg_mapping_iter mi, mo;
        unsigned int oi, oo; /* offset for in and out */
        unsigned long flags;
@@ -63,39 +65,51 @@ static int noinline_for_stack sun4i_ss_opti_poll(struct 
skcipher_request *areq)
        }
        writel(mode, ss->base + SS_CTL);
 
-       sg_miter_start(&mi, areq->src, sg_nents(areq->src),
-                      SG_MITER_FROM_SG | SG_MITER_ATOMIC);
-       sg_miter_start(&mo, areq->dst, sg_nents(areq->dst),
-                      SG_MITER_TO_SG | SG_MITER_ATOMIC);
-       sg_miter_next(&mi);
-       sg_miter_next(&mo);
-       if (!mi.addr || !mo.addr) {
-               dev_err_ratelimited(ss->dev, "ERROR: sg_miter return null\n");
-               err = -EINVAL;
-               goto release_ss;
-       }
 
        ileft = areq->cryptlen / 4;
        oleft = areq->cryptlen / 4;
        oi = 0;
        oo = 0;
        do {
-               todo = min(rx_cnt, ileft);
-               todo = min_t(size_t, todo, (mi.length - oi) / 4);
-               if (todo) {
-                       ileft -= todo;
-                       writesl(ss->base + SS_RXFIFO, mi.addr + oi, todo);
-                       oi += todo * 4;
-               }
-               if (oi == mi.length) {
-                       sg_miter_next(&mi);
-                       oi = 0;
+               if (ileft) {
+                       sg_miter_start(&mi, areq->src, sg_nents(areq->src),
+                                       SG_MITER_FROM_SG | SG_MITER_ATOMIC);
+                       if (pi)
+                               sg_miter_skip(&mi, pi);
+                       miter_err = sg_miter_next(&mi);
+                       if (!miter_err || !mi.addr) {
+                               dev_err_ratelimited(ss->dev, "ERROR: sg_miter 
return null\n");
+                               err = -EINVAL;
+                               goto release_ss;
+                       }
+                       todo = min(rx_cnt, ileft);
+                       todo = min_t(size_t, todo, (mi.length - oi) / 4);
+                       if (todo) {
+                               ileft -= todo;
+                               writesl(ss->base + SS_RXFIFO, mi.addr + oi, 
todo);
+                               oi += todo * 4;
+                       }
+                       if (oi == mi.length) {
+                               pi += mi.length;
+                               oi = 0;
+                       }
+                       sg_miter_stop(&mi);
                }
 
                spaces = readl(ss->base + SS_FCSR);
                rx_cnt = SS_RXFIFO_SPACES(spaces);
                tx_cnt = SS_TXFIFO_SPACES(spaces);
 
+               sg_miter_start(&mo, areq->dst, sg_nents(areq->dst),
+                              SG_MITER_TO_SG | SG_MITER_ATOMIC);
+               if (po)
+                       sg_miter_skip(&mo, po);
+               miter_err = sg_miter_next(&mo);
+               if (!miter_err || !mo.addr) {
+                       dev_err_ratelimited(ss->dev, "ERROR: sg_miter return 
null\n");
+                       err = -EINVAL;
+                       goto release_ss;
+               }
                todo = min(tx_cnt, oleft);
                todo = min_t(size_t, todo, (mo.length - oo) / 4);
                if (todo) {
@@ -104,9 +118,10 @@ static int noinline_for_stack sun4i_ss_opti_poll(struct 
skcipher_request *areq)
                        oo += todo * 4;
                }
                if (oo == mo.length) {
-                       sg_miter_next(&mo);
                        oo = 0;
+                       po += mo.length;
                }
+               sg_miter_stop(&mo);
        } while (oleft);
 
        if (areq->iv) {
@@ -120,8 +135,6 @@ static int noinline_for_stack sun4i_ss_opti_poll(struct 
skcipher_request *areq)
        }
 
 release_ss:
-       sg_miter_stop(&mi);
-       sg_miter_stop(&mo);
        writel(0, ss->base + SS_CTL);
        spin_unlock_irqrestore(&ss->slock, flags);
        return err;
@@ -174,6 +187,8 @@ static int sun4i_ss_cipher_poll(struct skcipher_request 
*areq)
        unsigned int todo;
        void *backup_iv = NULL;
        struct sg_mapping_iter mi, mo;
+       unsigned long pi = 0, po = 0; /* progress for in and out */
+       bool miter_err;
        unsigned int oi, oo;    /* offset for in and out */
        unsigned int ob = 0;    /* offset in buf */
        unsigned int obo = 0;   /* offset in bufo*/
@@ -234,17 +249,6 @@ static int sun4i_ss_cipher_poll(struct skcipher_request 
*areq)
        }
        writel(mode, ss->base + SS_CTL);
 
-       sg_miter_start(&mi, areq->src, sg_nents(areq->src),
-                      SG_MITER_FROM_SG | SG_MITER_ATOMIC);
-       sg_miter_start(&mo, areq->dst, sg_nents(areq->dst),
-                      SG_MITER_TO_SG | SG_MITER_ATOMIC);
-       sg_miter_next(&mi);
-       sg_miter_next(&mo);
-       if (!mi.addr || !mo.addr) {
-               dev_err_ratelimited(ss->dev, "ERROR: sg_miter return null\n");
-               err = -EINVAL;
-               goto release_ss;
-       }
        ileft = areq->cryptlen;
        oleft = areq->cryptlen;
        oi = 0;
@@ -252,6 +256,16 @@ static int sun4i_ss_cipher_poll(struct skcipher_request 
*areq)
 
        while (oleft) {
                if (ileft) {
+                       sg_miter_start(&mi, areq->src, sg_nents(areq->src),
+                                      SG_MITER_FROM_SG | SG_MITER_ATOMIC);
+                       if (pi)
+                               sg_miter_skip(&mi, pi);
+                       miter_err = sg_miter_next(&mi);
+                       if (!miter_err || !mi.addr) {
+                               dev_err_ratelimited(ss->dev, "ERROR: sg_miter 
return null\n");
+                               err = -EINVAL;
+                               goto release_ss;
+                       }
                        /*
                         * todo is the number of consecutive 4byte word that we
                         * can read from current SG
@@ -284,31 +298,38 @@ static int sun4i_ss_cipher_poll(struct skcipher_request 
*areq)
                                }
                        }
                        if (oi == mi.length) {
-                               sg_miter_next(&mi);
+                               pi += mi.length;
                                oi = 0;
                        }
+                       sg_miter_stop(&mi);
                }
 
                spaces = readl(ss->base + SS_FCSR);
                rx_cnt = SS_RXFIFO_SPACES(spaces);
                tx_cnt = SS_TXFIFO_SPACES(spaces);
-               dev_dbg(ss->dev,
-                       "%x %u/%zu %u/%u cnt=%u %u/%zu %u/%u cnt=%u %u\n",
-                       mode,
-                       oi, mi.length, ileft, areq->cryptlen, rx_cnt,
-                       oo, mo.length, oleft, areq->cryptlen, tx_cnt, ob);
 
                if (!tx_cnt)
                        continue;
+               sg_miter_start(&mo, areq->dst, sg_nents(areq->dst),
+                              SG_MITER_TO_SG | SG_MITER_ATOMIC);
+               if (po)
+                       sg_miter_skip(&mo, po);
+               miter_err = sg_miter_next(&mo);
+               if (!miter_err || !mo.addr) {
+                       dev_err_ratelimited(ss->dev, "ERROR: sg_miter return 
null\n");
+                       err = -EINVAL;
+                       goto release_ss;
+               }
                /* todo in 4bytes word */
                todo = min(tx_cnt, oleft / 4);
                todo = min_t(size_t, todo, (mo.length - oo) / 4);
+
                if (todo) {
                        readsl(ss->base + SS_TXFIFO, mo.addr + oo, todo);
                        oleft -= todo * 4;
                        oo += todo * 4;
                        if (oo == mo.length) {
-                               sg_miter_next(&mo);
+                               po += mo.length;
                                oo = 0;
                        }
                } else {
@@ -333,12 +354,14 @@ static int sun4i_ss_cipher_poll(struct skcipher_request 
*areq)
                                obo += todo;
                                oo += todo;
                                if (oo == mo.length) {
+                                       po += mo.length;
                                        sg_miter_next(&mo);
                                        oo = 0;
                                }
                        } while (obo < obl);
                        /* bufo must be fully used here */
                }
+               sg_miter_stop(&mo);
        }
        if (areq->iv) {
                if (mode & SS_DECRYPTION) {
@@ -351,8 +374,6 @@ static int sun4i_ss_cipher_poll(struct skcipher_request 
*areq)
        }
 
 release_ss:
-       sg_miter_stop(&mi);
-       sg_miter_stop(&mo);
        writel(0, ss->base + SS_CTL);
        spin_unlock_irqrestore(&ss->slock, flags);
 
-- 
2.26.2

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