vhost/crypto: handle virtually non-contiguous buffers
authorFan Zhang <roy.fan.zhang@intel.com>
Thu, 10 May 2018 15:41:22 +0000 (16:41 +0100)
committerFerruh Yigit <ferruh.yigit@intel.com>
Thu, 17 May 2018 10:29:05 +0000 (12:29 +0200)
This patch enables the handling of buffers non-contiguous in
virtual address space in the vhost_crypto. Instead of using
rte_vhost_va_from_guest_pa(), the host virtual address is
converted by vhost_iova_to_vva() for wider use cases.

For copy mode, the copy length is limited to the chunk size,
next chunks VAs being fetched afterward.

Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
lib/librte_vhost/vhost_crypto.c

index 4c25628..f165073 100644 (file)
@@ -42,7 +42,8 @@
                (1 << VIRTIO_CRYPTO_SERVICE_MAC) |                      \
                (1 << VIRTIO_NET_F_CTRL_VQ))
 
-#define GPA_TO_VVA(t, m, a, l) ((t)(uintptr_t)rte_vhost_va_from_guest_pa(m, a, l))
+#define IOVA_TO_VVA(t, r, a, l, p)                                     \
+       ((t)(uintptr_t)vhost_iova_to_vva(r->dev, r->vq, a, l, p))
 
 static int
 cipher_algo_transform(uint32_t virtio_cipher_algo)
@@ -216,7 +217,7 @@ struct vhost_crypto {
 
 struct vhost_crypto_data_req {
        struct vring_desc *head;
-       struct rte_vhost_memory *mem;
+       struct virtio_net *dev;
        struct virtio_crypto_inhdr *inhdr;
        struct vhost_virtqueue *vq;
        struct vring_desc *wb_desc;
@@ -473,18 +474,18 @@ find_write_desc(struct vring_desc *head, struct vring_desc *desc)
 }
 
 static struct virtio_crypto_inhdr *
-reach_inhdr(struct vring_desc *head, struct rte_vhost_memory *mem,
-               struct vring_desc *desc)
+reach_inhdr(struct vhost_crypto_data_req *vc_req, struct vring_desc *desc)
 {
        uint64_t dlen;
        struct virtio_crypto_inhdr *inhdr;
 
        while (desc->flags & VRING_DESC_F_NEXT)
-               desc = &head[desc->next];
+               desc = &vc_req->head[desc->next];
 
        dlen = desc->len;
-       inhdr = GPA_TO_VVA(struct virtio_crypto_inhdr *, mem, desc->addr, &dlen);
-       if (unlikely(dlen != desc->len))
+       inhdr = IOVA_TO_VVA(struct virtio_crypto_inhdr *, vc_req, desc->addr,
+                       &dlen, VHOST_ACCESS_WO);
+       if (unlikely(!inhdr || dlen != desc->len))
                return NULL;
 
        return inhdr;
@@ -516,40 +517,86 @@ move_desc(struct vring_desc *head, struct vring_desc **cur_desc,
 }
 
 static int
-copy_data(void *dst_data, struct vring_desc *head, struct rte_vhost_memory *mem,
+copy_data(void *dst_data, struct vhost_crypto_data_req *vc_req,
                struct vring_desc **cur_desc, uint32_t size)
 {
        struct vring_desc *desc = *cur_desc;
+       uint64_t remain, addr, dlen, len;
        uint32_t to_copy;
        uint8_t *data = dst_data;
        uint8_t *src;
        int left = size;
-       uint64_t dlen;
 
-       rte_prefetch0(&head[desc->next]);
+       rte_prefetch0(&vc_req->head[desc->next]);
        to_copy = RTE_MIN(desc->len, (uint32_t)left);
-       dlen = desc->len;
-       src = GPA_TO_VVA(uint8_t *, mem, desc->addr, &dlen);
-       if (unlikely(!src || dlen != desc->len)) {
+       dlen = to_copy;
+       src = IOVA_TO_VVA(uint8_t *, vc_req, desc->addr, &dlen,
+                       VHOST_ACCESS_RO);
+       if (unlikely(!src || !dlen)) {
                VC_LOG_ERR("Failed to map descriptor");
                return -1;
        }
 
-       rte_memcpy((uint8_t *)data, src, to_copy);
+       rte_memcpy((uint8_t *)data, src, dlen);
+       data += dlen;
+
+       if (unlikely(dlen < to_copy)) {
+               remain = to_copy - dlen;
+               addr = desc->addr + dlen;
+
+               while (remain) {
+                       len = remain;
+                       src = IOVA_TO_VVA(uint8_t *, vc_req, addr, &len,
+                                       VHOST_ACCESS_RO);
+                       if (unlikely(!src || !len)) {
+                               VC_LOG_ERR("Failed to map descriptor");
+                               return -1;
+                       }
+
+                       rte_memcpy(data, src, len);
+                       addr += len;
+                       remain -= len;
+                       data += len;
+               }
+       }
+
        left -= to_copy;
 
        while ((desc->flags & VRING_DESC_F_NEXT) && left > 0) {
-               desc = &head[desc->next];
-               rte_prefetch0(&head[desc->next]);
+               desc = &vc_req->head[desc->next];
+               rte_prefetch0(&vc_req->head[desc->next]);
                to_copy = RTE_MIN(desc->len, (uint32_t)left);
                dlen = desc->len;
-               src = GPA_TO_VVA(uint8_t *, mem, desc->addr, &dlen);
-               if (unlikely(!src || dlen != desc->len)) {
+               src = IOVA_TO_VVA(uint8_t *, vc_req, desc->addr, &dlen,
+                               VHOST_ACCESS_RO);
+               if (unlikely(!src || !dlen)) {
                        VC_LOG_ERR("Failed to map descriptor");
                        return -1;
                }
 
-               rte_memcpy(data + size - left, src, to_copy);
+               rte_memcpy(data, src, dlen);
+               data += dlen;
+
+               if (unlikely(dlen < to_copy)) {
+                       remain = to_copy - dlen;
+                       addr = desc->addr + dlen;
+
+                       while (remain) {
+                               len = remain;
+                               src = IOVA_TO_VVA(uint8_t *, vc_req, addr, &len,
+                                               VHOST_ACCESS_RO);
+                               if (unlikely(!src || !len)) {
+                                       VC_LOG_ERR("Failed to map descriptor");
+                                       return -1;
+                               }
+
+                               rte_memcpy(data, src, len);
+                               addr += len;
+                               remain -= len;
+                               data += len;
+                       }
+               }
+
                left -= to_copy;
        }
 
@@ -558,25 +605,25 @@ copy_data(void *dst_data, struct vring_desc *head, struct rte_vhost_memory *mem,
                return -1;
        }
 
-       *cur_desc = &head[desc->next];
+       *cur_desc = &vc_req->head[desc->next];
 
        return 0;
 }
 
 static __rte_always_inline void *
-get_data_ptr(struct vring_desc *head, struct rte_vhost_memory *mem,
-               struct vring_desc **cur_desc, uint32_t size)
+get_data_ptr(struct vhost_crypto_data_req *vc_req, struct vring_desc **cur_desc,
+               uint32_t size, uint8_t perm)
 {
        void *data;
        uint64_t dlen = (*cur_desc)->len;
 
-       data = GPA_TO_VVA(void *, mem, (*cur_desc)->addr, &dlen);
+       data = IOVA_TO_VVA(void *, vc_req, (*cur_desc)->addr, &dlen, perm);
        if (unlikely(!data || dlen != (*cur_desc)->len)) {
                VC_LOG_ERR("Failed to map object");
                return NULL;
        }
 
-       if (unlikely(move_desc(head, cur_desc, size) < 0))
+       if (unlikely(move_desc(vc_req->head, cur_desc, size) < 0))
                return NULL;
 
        return data;
@@ -587,7 +634,6 @@ write_back_data(struct rte_crypto_op *op, struct vhost_crypto_data_req *vc_req)
 {
        struct rte_mbuf *mbuf = op->sym->m_dst;
        struct vring_desc *head = vc_req->head;
-       struct rte_vhost_memory *mem = vc_req->mem;
        struct vring_desc *desc = vc_req->wb_desc;
        int left = vc_req->wb_len;
        uint32_t to_write;
@@ -597,7 +643,8 @@ write_back_data(struct rte_crypto_op *op, struct vhost_crypto_data_req *vc_req)
        rte_prefetch0(&head[desc->next]);
        to_write = RTE_MIN(desc->len, (uint32_t)left);
        dlen = desc->len;
-       dst = GPA_TO_VVA(uint8_t *, mem, desc->addr, &dlen);
+       dst = IOVA_TO_VVA(uint8_t *, vc_req, desc->addr, &dlen,
+                       VHOST_ACCESS_RW);
        if (unlikely(!dst || dlen != desc->len)) {
                VC_LOG_ERR("Failed to map descriptor");
                return -1;
@@ -612,7 +659,8 @@ write_back_data(struct rte_crypto_op *op, struct vhost_crypto_data_req *vc_req)
                rte_prefetch0(&head[desc->next]);
                to_write = RTE_MIN(desc->len, (uint32_t)left);
                dlen = desc->len;
-               dst = GPA_TO_VVA(uint8_t *, mem, desc->addr, &dlen);
+               dst = IOVA_TO_VVA(uint8_t *, vc_req, desc->addr, &dlen,
+                               VHOST_ACCESS_RW);
                if (unlikely(!dst || dlen != desc->len)) {
                        VC_LOG_ERR("Failed to map descriptor");
                        return -1;
@@ -637,16 +685,14 @@ prepare_sym_cipher_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
                struct virtio_crypto_cipher_data_req *cipher,
                struct vring_desc *cur_desc)
 {
-       struct vring_desc *head = vc_req->head;
        struct vring_desc *desc = cur_desc;
-       struct rte_vhost_memory *mem = vc_req->mem;
        struct rte_mbuf *m_src = op->sym->m_src, *m_dst = op->sym->m_dst;
        uint8_t *iv_data = rte_crypto_op_ctod_offset(op, uint8_t *, IV_OFFSET);
        uint8_t ret = 0;
 
        /* prepare */
        /* iv */
-       if (unlikely(copy_data(iv_data, head, mem, &desc,
+       if (unlikely(copy_data(iv_data, vc_req, &desc,
                        cipher->para.iv_len) < 0)) {
                ret = VIRTIO_CRYPTO_BADMSG;
                goto error_exit;
@@ -658,8 +704,8 @@ prepare_sym_cipher_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        case RTE_VHOST_CRYPTO_ZERO_COPY_ENABLE:
                m_src->buf_iova = gpa_to_hpa(vcrypto->dev, desc->addr,
                                cipher->para.src_data_len);
-               m_src->buf_addr = get_data_ptr(head, mem, &desc,
-                               cipher->para.src_data_len);
+               m_src->buf_addr = get_data_ptr(vc_req, &desc,
+                               cipher->para.src_data_len, VHOST_ACCESS_RO);
                if (unlikely(m_src->buf_iova == 0 ||
                                m_src->buf_addr == NULL)) {
                        VC_LOG_ERR("zero_copy may fail due to cross page data");
@@ -674,8 +720,8 @@ prepare_sym_cipher_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
                        ret = VIRTIO_CRYPTO_ERR;
                        goto error_exit;
                }
-               if (unlikely(copy_data(rte_pktmbuf_mtod(m_src, uint8_t *), head,
-                               mem, &desc, cipher->para.src_data_len)
+               if (unlikely(copy_data(rte_pktmbuf_mtod(m_src, uint8_t *),
+                               vc_req, &desc, cipher->para.src_data_len)
                                < 0)) {
                        ret = VIRTIO_CRYPTO_BADMSG;
                        goto error_exit;
@@ -687,7 +733,7 @@ prepare_sym_cipher_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        }
 
        /* dst */
-       desc = find_write_desc(head, desc);
+       desc = find_write_desc(vc_req->head, desc);
        if (unlikely(!desc)) {
                VC_LOG_ERR("Cannot find write location");
                ret = VIRTIO_CRYPTO_BADMSG;
@@ -698,8 +744,8 @@ prepare_sym_cipher_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        case RTE_VHOST_CRYPTO_ZERO_COPY_ENABLE:
                m_dst->buf_iova = gpa_to_hpa(vcrypto->dev,
                                desc->addr, cipher->para.dst_data_len);
-               m_dst->buf_addr = get_data_ptr(head, mem, &desc,
-                               cipher->para.dst_data_len);
+               m_dst->buf_addr = get_data_ptr(vc_req, &desc,
+                               cipher->para.dst_data_len, VHOST_ACCESS_RW);
                if (unlikely(m_dst->buf_iova == 0 || m_dst->buf_addr == NULL)) {
                        VC_LOG_ERR("zero_copy may fail due to cross page data");
                        ret = VIRTIO_CRYPTO_ERR;
@@ -711,7 +757,8 @@ prepare_sym_cipher_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        case RTE_VHOST_CRYPTO_ZERO_COPY_DISABLE:
                vc_req->wb_desc = desc;
                vc_req->wb_len = cipher->para.dst_data_len;
-               if (unlikely(move_desc(head, &desc, vc_req->wb_len) < 0)) {
+               if (unlikely(move_desc(vc_req->head, &desc,
+                               vc_req->wb_len) < 0)) {
                        ret = VIRTIO_CRYPTO_ERR;
                        goto error_exit;
                }
@@ -728,7 +775,7 @@ prepare_sym_cipher_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        op->sym->cipher.data.offset = 0;
        op->sym->cipher.data.length = cipher->para.src_data_len;
 
-       vc_req->inhdr = get_data_ptr(head, mem, &desc, INHDR_LEN);
+       vc_req->inhdr = get_data_ptr(vc_req, &desc, INHDR_LEN, VHOST_ACCESS_WO);
        if (unlikely(vc_req->inhdr == NULL)) {
                ret = VIRTIO_CRYPTO_BADMSG;
                goto error_exit;
@@ -750,9 +797,7 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
                struct virtio_crypto_alg_chain_data_req *chain,
                struct vring_desc *cur_desc)
 {
-       struct vring_desc *head = vc_req->head;
        struct vring_desc *desc = cur_desc;
-       struct rte_vhost_memory *mem = vc_req->mem;
        struct rte_mbuf *m_src = op->sym->m_src, *m_dst = op->sym->m_dst;
        uint8_t *iv_data = rte_crypto_op_ctod_offset(op, uint8_t *, IV_OFFSET);
        uint32_t digest_offset;
@@ -761,7 +806,7 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
 
        /* prepare */
        /* iv */
-       if (unlikely(copy_data(iv_data, head, mem, &desc,
+       if (unlikely(copy_data(iv_data, vc_req, &desc,
                        chain->para.iv_len) < 0)) {
                ret = VIRTIO_CRYPTO_BADMSG;
                goto error_exit;
@@ -774,8 +819,8 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        case RTE_VHOST_CRYPTO_ZERO_COPY_ENABLE:
                m_src->buf_iova = gpa_to_hpa(vcrypto->dev, desc->addr,
                                chain->para.src_data_len);
-               m_src->buf_addr = get_data_ptr(head, mem, &desc,
-                               chain->para.src_data_len);
+               m_src->buf_addr = get_data_ptr(vc_req, &desc,
+                               chain->para.src_data_len, VHOST_ACCESS_RO);
                if (unlikely(m_src->buf_iova == 0 || m_src->buf_addr == NULL)) {
                        VC_LOG_ERR("zero_copy may fail due to cross page data");
                        ret = VIRTIO_CRYPTO_ERR;
@@ -789,8 +834,8 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
                        ret = VIRTIO_CRYPTO_ERR;
                        goto error_exit;
                }
-               if (unlikely(copy_data(rte_pktmbuf_mtod(m_src, uint8_t *), head,
-                               mem, &desc, chain->para.src_data_len)) < 0) {
+               if (unlikely(copy_data(rte_pktmbuf_mtod(m_src, uint8_t *),
+                               vc_req, &desc, chain->para.src_data_len)) < 0) {
                        ret = VIRTIO_CRYPTO_BADMSG;
                        goto error_exit;
                }
@@ -801,7 +846,7 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        }
 
        /* dst */
-       desc = find_write_desc(head, desc);
+       desc = find_write_desc(vc_req->head, desc);
        if (unlikely(!desc)) {
                VC_LOG_ERR("Cannot find write location");
                ret = VIRTIO_CRYPTO_BADMSG;
@@ -812,8 +857,8 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        case RTE_VHOST_CRYPTO_ZERO_COPY_ENABLE:
                m_dst->buf_iova = gpa_to_hpa(vcrypto->dev,
                                desc->addr, chain->para.dst_data_len);
-               m_dst->buf_addr = get_data_ptr(head, mem, &desc,
-                               chain->para.dst_data_len);
+               m_dst->buf_addr = get_data_ptr(vc_req, &desc,
+                               chain->para.dst_data_len, VHOST_ACCESS_RW);
                if (unlikely(m_dst->buf_iova == 0 || m_dst->buf_addr == NULL)) {
                        VC_LOG_ERR("zero_copy may fail due to cross page data");
                        ret = VIRTIO_CRYPTO_ERR;
@@ -822,8 +867,8 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
 
                op->sym->auth.digest.phys_addr = gpa_to_hpa(vcrypto->dev,
                                desc->addr, chain->para.hash_result_len);
-               op->sym->auth.digest.data = get_data_ptr(head, mem, &desc,
-                               chain->para.hash_result_len);
+               op->sym->auth.digest.data = get_data_ptr(vc_req, &desc,
+                               chain->para.hash_result_len, VHOST_ACCESS_RW);
                if (unlikely(op->sym->auth.digest.phys_addr == 0)) {
                        VC_LOG_ERR("zero_copy may fail due to cross page data");
                        ret = VIRTIO_CRYPTO_ERR;
@@ -838,13 +883,13 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
                vc_req->wb_desc = desc;
                vc_req->wb_len = m_dst->data_len + chain->para.hash_result_len;
 
-               if (unlikely(move_desc(head, &desc,
+               if (unlikely(move_desc(vc_req->head, &desc,
                                chain->para.dst_data_len) < 0)) {
                        ret = VIRTIO_CRYPTO_BADMSG;
                        goto error_exit;
                }
 
-               if (unlikely(copy_data(digest_addr, head, mem, &desc,
+               if (unlikely(copy_data(digest_addr, vc_req, &desc,
                                chain->para.hash_result_len)) < 0) {
                        ret = VIRTIO_CRYPTO_BADMSG;
                        goto error_exit;
@@ -860,7 +905,7 @@ prepare_sym_chain_op(struct vhost_crypto *vcrypto, struct rte_crypto_op *op,
        }
 
        /* record inhdr */
-       vc_req->inhdr = get_data_ptr(head, mem, &desc, INHDR_LEN);
+       vc_req->inhdr = get_data_ptr(vc_req, &desc, INHDR_LEN, VHOST_ACCESS_WO);
        if (unlikely(vc_req->inhdr == NULL)) {
                ret = VIRTIO_CRYPTO_BADMSG;
                goto error_exit;
@@ -893,13 +938,12 @@ error_exit:
 static __rte_always_inline int
 vhost_crypto_process_one_req(struct vhost_crypto *vcrypto,
                struct vhost_virtqueue *vq, struct rte_crypto_op *op,
-               struct vring_desc *head, uint16_t desc_idx,
-               struct rte_vhost_memory *mem)
+               struct vring_desc *head, uint16_t desc_idx)
 {
        struct vhost_crypto_data_req *vc_req = RTE_PTR_ADD(op->sym->m_src,
                        sizeof(struct rte_mbuf));
        struct rte_cryptodev_sym_session *session;
-       struct virtio_crypto_op_data_req *req;
+       struct virtio_crypto_op_data_req *req, tmp_req;
        struct virtio_crypto_inhdr *inhdr;
        struct vring_desc *desc = NULL;
        uint64_t session_id;
@@ -907,10 +951,13 @@ vhost_crypto_process_one_req(struct vhost_crypto *vcrypto,
        int err = 0;
 
        vc_req->desc_idx = desc_idx;
+       vc_req->dev = vcrypto->dev;
+       vc_req->vq = vq;
 
        if (likely(head->flags & VRING_DESC_F_INDIRECT)) {
                dlen = head->len;
-               desc = GPA_TO_VVA(struct vring_desc *, mem, head->addr, &dlen);
+               desc = IOVA_TO_VVA(struct vring_desc *, vc_req, head->addr,
+                               &dlen, VHOST_ACCESS_RO);
                if (unlikely(!desc || dlen != head->len))
                        return -1;
                desc_idx = 0;
@@ -919,17 +966,30 @@ vhost_crypto_process_one_req(struct vhost_crypto *vcrypto,
                desc = head;
        }
 
-       vc_req->mem = mem;
        vc_req->head = head;
-       vc_req->vq = vq;
-
        vc_req->zero_copy = vcrypto->option;
 
-       req = get_data_ptr(head, mem, &desc, sizeof(*req));
+       req = get_data_ptr(vc_req, &desc, sizeof(*req), VHOST_ACCESS_RO);
        if (unlikely(req == NULL)) {
-               err = VIRTIO_CRYPTO_ERR;
-               VC_LOG_ERR("Invalid descriptor");
-               goto error_exit;
+               switch (vcrypto->option) {
+               case RTE_VHOST_CRYPTO_ZERO_COPY_ENABLE:
+                       err = VIRTIO_CRYPTO_BADMSG;
+                       VC_LOG_ERR("Invalid descriptor");
+                       goto error_exit;
+               case RTE_VHOST_CRYPTO_ZERO_COPY_DISABLE:
+                       req = &tmp_req;
+                       if (unlikely(copy_data(req, vc_req, &desc, sizeof(*req))
+                                       < 0)) {
+                               err = VIRTIO_CRYPTO_BADMSG;
+                               VC_LOG_ERR("Invalid descriptor");
+                               goto error_exit;
+                       }
+                       break;
+               default:
+                       err = VIRTIO_CRYPTO_ERR;
+                       VC_LOG_ERR("Invalid option");
+                       goto error_exit;
+               }
        }
 
        switch (req->header.opcode) {
@@ -989,7 +1049,7 @@ vhost_crypto_process_one_req(struct vhost_crypto *vcrypto,
 
 error_exit:
 
-       inhdr = reach_inhdr(head, mem, desc);
+       inhdr = reach_inhdr(vc_req, desc);
        if (likely(inhdr != NULL))
                inhdr->status = (uint8_t)err;
 
@@ -1216,7 +1276,6 @@ rte_vhost_crypto_fetch_requests(int vid, uint32_t qid,
 {
        struct rte_mbuf *mbufs[VHOST_CRYPTO_MAX_BURST_SIZE * 2];
        struct virtio_net *dev = get_device(vid);
-       struct rte_vhost_memory *mem;
        struct vhost_crypto *vcrypto;
        struct vhost_virtqueue *vq;
        uint16_t avail_idx;
@@ -1242,7 +1301,6 @@ rte_vhost_crypto_fetch_requests(int vid, uint32_t qid,
        }
 
        vq = dev->virtqueue[qid];
-       mem = dev->mem;
 
        avail_idx = *((volatile uint16_t *)&vq->avail->idx);
        start_idx = vq->last_used_idx;
@@ -1275,7 +1333,7 @@ rte_vhost_crypto_fetch_requests(int vid, uint32_t qid,
                op->sym->m_dst->data_off = 0;
 
                if (unlikely(vhost_crypto_process_one_req(vcrypto, vq, op, head,
-                               desc_idx, mem)) < 0)
+                               desc_idx)) < 0)
                        break;
        }