crypto: qat - use pre-allocated buffers in datapath

In order to do DMAs, the QAT device requires that the scatterlist
structures are mapped and translated into a format that the firmware can
understand. This is defined as the composition of a scatter gather list
(SGL) descriptor header, the struct qat_alg_buf_list, plus a variable
number of flat buffer descriptors, the struct qat_alg_buf.

The allocation and mapping of these data structures is done each time a
request is received from the skcipher and aead APIs.
In an OOM situation, this behaviour might lead to a dead-lock if an
allocation fails.

Based on the conversation in [1], increase the size of the aead and
skcipher request contexts to include an SGL descriptor that can handle
a maximum of 4 flat buffers.
If requests exceed 4 entries buffers, memory is allocated dynamically.

[1] https://lore.kernel.org/linux-crypto/20200722072932.GA27544@gondor.apana.org.au/

Cc: stable@vger.kernel.org
Fixes: d370cec3 ("crypto: qat - Intel(R) QAT crypto interface")
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Marco Chiappero <marco.chiappero@intel.com>
Reviewed-by: Wojciech Ziemba <wojciech.ziemba@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/qat/qat_common/qat_algs.c

@@ -46,19 +46,6 @@
 static DEFINE_MUTEX(algs_lock);
 static unsigned int active_devs;
 
-struct qat_alg_buf {
-	u32 len;
-	u32 resrvd;
-	u64 addr;
-} __packed;
-
-struct qat_alg_buf_list {
-	u64 resrvd;
-	u32 num_bufs;
-	u32 num_mapped_bufs;
-	struct qat_alg_buf bufers[];
-} __packed __aligned(64);
-
 /* Common content descriptor */
 struct qat_alg_cd {
 	union {
@@ -693,7 +680,10 @@ static void qat_alg_free_bufl(struct qat_crypto_instance *inst,
 				 bl->bufers[i].len, DMA_BIDIRECTIONAL);
 
 	dma_unmap_single(dev, blp, sz, DMA_TO_DEVICE);
-	kfree(bl);
+
+	if (!qat_req->buf.sgl_src_valid)
+		kfree(bl);
+
 	if (blp != blpout) {
 		/* If out of place operation dma unmap only data */
 		int bufless = blout->num_bufs - blout->num_mapped_bufs;
@@ -704,7 +694,9 @@ static void qat_alg_free_bufl(struct qat_crypto_instance *inst,
 					 DMA_BIDIRECTIONAL);
 		}
 		dma_unmap_single(dev, blpout, sz_out, DMA_TO_DEVICE);
-		kfree(blout);
+
+		if (!qat_req->buf.sgl_dst_valid)
+			kfree(blout);
 	}
 }
 
@@ -721,15 +713,24 @@ static int qat_alg_sgl_to_bufl(struct qat_crypto_instance *inst,
 	dma_addr_t blp = DMA_MAPPING_ERROR;
 	dma_addr_t bloutp = DMA_MAPPING_ERROR;
 	struct scatterlist *sg;
-	size_t sz_out, sz = struct_size(bufl, bufers, n + 1);
+	size_t sz_out, sz = struct_size(bufl, bufers, n);
+	int node = dev_to_node(&GET_DEV(inst->accel_dev));
 
 	if (unlikely(!n))
 		return -EINVAL;
 
-	bufl = kzalloc_node(sz, GFP_ATOMIC,
-			    dev_to_node(&GET_DEV(inst->accel_dev)));
-	if (unlikely(!bufl))
-		return -ENOMEM;
+	qat_req->buf.sgl_src_valid = false;
+	qat_req->buf.sgl_dst_valid = false;
+
+	if (n > QAT_MAX_BUFF_DESC) {
+		bufl = kzalloc_node(sz, GFP_ATOMIC, node);
+		if (unlikely(!bufl))
+			return -ENOMEM;
+	} else {
+		bufl = &qat_req->buf.sgl_src.sgl_hdr;
+		memset(bufl, 0, sizeof(struct qat_alg_buf_list));
+		qat_req->buf.sgl_src_valid = true;
+	}
 
 	for_each_sg(sgl, sg, n, i)
 		bufl->bufers[i].addr = DMA_MAPPING_ERROR;
@@ -760,12 +761,18 @@ static int qat_alg_sgl_to_bufl(struct qat_crypto_instance *inst,
 		struct qat_alg_buf *bufers;
 
 		n = sg_nents(sglout);
-		sz_out = struct_size(buflout, bufers, n + 1);
+		sz_out = struct_size(buflout, bufers, n);
 		sg_nctr = 0;
-		buflout = kzalloc_node(sz_out, GFP_ATOMIC,
-				       dev_to_node(&GET_DEV(inst->accel_dev)));
-		if (unlikely(!buflout))
-			goto err_in;
+
+		if (n > QAT_MAX_BUFF_DESC) {
+			buflout = kzalloc_node(sz_out, GFP_ATOMIC, node);
+			if (unlikely(!buflout))
+				goto err_in;
+		} else {
+			buflout = &qat_req->buf.sgl_dst.sgl_hdr;
+			memset(buflout, 0, sizeof(struct qat_alg_buf_list));
+			qat_req->buf.sgl_dst_valid = true;
+		}
 
 		bufers = buflout->bufers;
 		for_each_sg(sglout, sg, n, i)
@@ -810,7 +817,9 @@ static int qat_alg_sgl_to_bufl(struct qat_crypto_instance *inst,
 			dma_unmap_single(dev, buflout->bufers[i].addr,
 					 buflout->bufers[i].len,
 					 DMA_BIDIRECTIONAL);
-	kfree(buflout);
+
+	if (!qat_req->buf.sgl_dst_valid)
+		kfree(buflout);
 
 err_in:
 	if (!dma_mapping_error(dev, blp))
@@ -823,7 +832,8 @@ static int qat_alg_sgl_to_bufl(struct qat_crypto_instance *inst,
 					 bufl->bufers[i].len,
 					 DMA_BIDIRECTIONAL);
 
-	kfree(bufl);
+	if (!qat_req->buf.sgl_src_valid)
+		kfree(bufl);
 
 	dev_err(dev, "Failed to map buf for dma\n");
 	return -ENOMEM;

drivers/crypto/qat/qat_common/qat_crypto.h

@@ -21,6 +21,26 @@ struct qat_crypto_instance {
 	atomic_t refctr;
 };
 
+#define QAT_MAX_BUFF_DESC	4
+
+struct qat_alg_buf {
+	u32 len;
+	u32 resrvd;
+	u64 addr;
+} __packed;
+
+struct qat_alg_buf_list {
+	u64 resrvd;
+	u32 num_bufs;
+	u32 num_mapped_bufs;
+	struct qat_alg_buf bufers[];
+} __packed;
+
+struct qat_alg_fixed_buf_list {
+	struct qat_alg_buf_list sgl_hdr;
+	struct qat_alg_buf descriptors[QAT_MAX_BUFF_DESC];
+} __packed __aligned(64);
+
 struct qat_crypto_request_buffs {
 	struct qat_alg_buf_list *bl;
 	dma_addr_t blp;
@@ -28,6 +48,10 @@ struct qat_crypto_request_buffs {
 	dma_addr_t bloutp;
 	size_t sz;
 	size_t sz_out;
+	bool sgl_src_valid;
+	bool sgl_dst_valid;
+	struct qat_alg_fixed_buf_list sgl_src;
+	struct qat_alg_fixed_buf_list sgl_dst;
 };
 
 struct qat_crypto_request;