From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Date: Mon, 27 Jan 2020 19:01:03 +0000

Subject: [PATCH] virtiofsd: Send replies to messages

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

Route fuse out messages back through the same queue elements

that had the command that triggered the request.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit df57ba919ec3edef9cc208d35685095e6e92713e)

---

 tools/virtiofsd/fuse_lowlevel.c |   4 ++

 tools/virtiofsd/fuse_virtio.c   | 107 ++++++++++++++++++++++++++++++--

 tools/virtiofsd/fuse_virtio.h   |   4 ++

 3 files changed, 111 insertions(+), 4 deletions(-)

diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c

index af09fa2b94..380d93bd01 100644

--- a/tools/virtiofsd/fuse_lowlevel.c

+++ b/tools/virtiofsd/fuse_lowlevel.c

@@ -171,6 +171,10 @@ static int fuse_send_msg(struct fuse_session *se, struct fuse_chan *ch,

         }

     }

+    if (fuse_lowlevel_is_virtio(se)) {

+        return virtio_send_msg(se, ch, iov, count);

+    }

+

     abort(); /* virtio should have taken it before here */

     return 0;

 }

diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c

index 3841b20129..05d0e29f12 100644

--- a/tools/virtiofsd/fuse_virtio.c

+++ b/tools/virtiofsd/fuse_virtio.c

@@ -41,6 +41,9 @@ struct fv_QueueInfo {

     /* Our queue index, corresponds to array position */

     int qidx;

     int kick_fd;

+

+    /* The element for the command currently being processed */

+    VuVirtqElement *qe;

 };

 /*

@@ -121,6 +124,105 @@ static void copy_from_iov(struct fuse_buf *buf, size_t out_num,

     }

 }

+/*

+ * Copy from one iov to another, the given number of bytes

+ * The caller must have checked sizes.

+ */

+static void copy_iov(struct iovec *src_iov, int src_count,

+                     struct iovec *dst_iov, int dst_count, size_t to_copy)

+{

+    size_t dst_offset = 0;

+    /* Outer loop copies 'src' elements */

+    while (to_copy) {

+        assert(src_count);

+        size_t src_len = src_iov[0].iov_len;

+        size_t src_offset = 0;

+

+        if (src_len > to_copy) {

+            src_len = to_copy;

+        }

+        /* Inner loop copies contents of one 'src' to maybe multiple dst. */

+        while (src_len) {

+            assert(dst_count);

+            size_t dst_len = dst_iov[0].iov_len - dst_offset;

+            if (dst_len > src_len) {

+                dst_len = src_len;

+            }

+

+            memcpy(dst_iov[0].iov_base + dst_offset,

+                   src_iov[0].iov_base + src_offset, dst_len);

+            src_len -= dst_len;

+            to_copy -= dst_len;

+            src_offset += dst_len;

+            dst_offset += dst_len;

+

+            assert(dst_offset <= dst_iov[0].iov_len);

+            if (dst_offset == dst_iov[0].iov_len) {

+                dst_offset = 0;

+                dst_iov++;

+                dst_count--;

+            }

+        }

+        src_iov++;

+        src_count--;

+    }

+}

+

+/*

+ * Called back by ll whenever it wants to send a reply/message back

+ * The 1st element of the iov starts with the fuse_out_header

+ * 'unique'==0 means it's a notify message.

+ */

+int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,

+                    struct iovec *iov, int count)

+{

+    VuVirtqElement *elem;

+    VuVirtq *q;

+

+    assert(count >= 1);

+    assert(iov[0].iov_len >= sizeof(struct fuse_out_header));

+

+    struct fuse_out_header *out = iov[0].iov_base;

+    /* TODO: Endianness! */

+

+    size_t tosend_len = iov_size(iov, count);

+

+    /* unique == 0 is notification, which we don't support */

+    assert(out->unique);

+    /* For virtio we always have ch */

+    assert(ch);

+    elem = ch->qi->qe;

+    q = &ch->qi->virtio_dev->dev.vq[ch->qi->qidx];

+

+    /* The 'in' part of the elem is to qemu */

+    unsigned int in_num = elem->in_num;

+    struct iovec *in_sg = elem->in_sg;

+    size_t in_len = iov_size(in_sg, in_num);

+    fuse_log(FUSE_LOG_DEBUG, "%s: elem %d: with %d in desc of length %zd\n",

+             __func__, elem->index, in_num, in_len);

+

+    /*

+     * The elem should have room for a 'fuse_out_header' (out from fuse)

+     * plus the data based on the len in the header.

+     */

+    if (in_len < sizeof(struct fuse_out_header)) {

+        fuse_log(FUSE_LOG_ERR, "%s: elem %d too short for out_header\n",

+                 __func__, elem->index);

+        return -E2BIG;

+    }

+    if (in_len < tosend_len) {

+        fuse_log(FUSE_LOG_ERR, "%s: elem %d too small for data len %zd\n",

+                 __func__, elem->index, tosend_len);

+        return -E2BIG;

+    }

+

+    copy_iov(iov, count, in_sg, in_num, tosend_len);

+    vu_queue_push(&se->virtio_dev->dev, q, elem, tosend_len);

+    vu_queue_notify(&se->virtio_dev->dev, q);

+

+    return 0;

+}

+

 /* Thread function for individual queues, created when a queue is 'started' */

 static void *fv_queue_thread(void *opaque)

 {

@@ -226,13 +328,10 @@ static void *fv_queue_thread(void *opaque)

             /* TODO! Endianness of header */

-            /* TODO: Fixup fuse_send_msg */

             /* TODO: Add checks for fuse_session_exited */

             fuse_session_process_buf_int(se, &fbuf, &ch);

-            /* TODO: vu_queue_push(dev, q, elem, qi->write_count); */

-            vu_queue_notify(dev, q);

-

+            qi->qe = NULL;

             free(elem);

             elem = NULL;

         }

diff --git a/tools/virtiofsd/fuse_virtio.h b/tools/virtiofsd/fuse_virtio.h

index 23026d6e4c..135a14875a 100644

--- a/tools/virtiofsd/fuse_virtio.h

+++ b/tools/virtiofsd/fuse_virtio.h

@@ -22,4 +22,8 @@ int virtio_session_mount(struct fuse_session *se);

 int virtio_loop(struct fuse_session *se);

+

+int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,

+                    struct iovec *iov, int count);

+

 #endif