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

Date: Mon, 27 Jan 2020 19:01:02 +0000

Subject: [PATCH] virtiofsd: Start reading commands from queue

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Pop queue elements off queues, copy the data from them and

pass that to fuse.

  Note: 'out' in a VuVirtqElement is from QEMU

        'in' in libfuse is into the daemon

  So we read from the out iov's to get a fuse_in_header

When we get a kick we've got to read all the elements until the queue

is empty.

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 b509e1228b3e5eb83c14819045988999fc2dbd1b)

---

 tools/virtiofsd/fuse_i.h      |  2 +

 tools/virtiofsd/fuse_virtio.c | 99 +++++++++++++++++++++++++++++++++--

 2 files changed, 98 insertions(+), 3 deletions(-)

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

index ec04449069..1126723d18 100644

--- a/tools/virtiofsd/fuse_i.h

+++ b/tools/virtiofsd/fuse_i.h

@@ -14,6 +14,7 @@

 #include "fuse_lowlevel.h"

 struct fv_VuDev;

+struct fv_QueueInfo;

 struct fuse_req {

     struct fuse_session *se;

@@ -75,6 +76,7 @@ struct fuse_chan {

     pthread_mutex_t lock;

     int ctr;

     int fd;

+    struct fv_QueueInfo *qi;

 };

 /**

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

index 05e7258712..3841b20129 100644

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

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

@@ -12,6 +12,7 @@

  */

 #include "qemu/osdep.h"

+#include "qemu/iov.h"

 #include "fuse_virtio.h"

 #include "fuse_i.h"

 #include "standard-headers/linux/fuse.h"

@@ -32,6 +33,7 @@

 #include "contrib/libvhost-user/libvhost-user.h"

+struct fv_VuDev;

 struct fv_QueueInfo {

     pthread_t thread;

     struct fv_VuDev *virtio_dev;

@@ -101,10 +103,41 @@ static void fv_panic(VuDev *dev, const char *err)

     exit(EXIT_FAILURE);

 }

+/*

+ * Copy from an iovec into a fuse_buf (memory only)

+ * Caller must ensure there is space

+ */

+static void copy_from_iov(struct fuse_buf *buf, size_t out_num,

+                          const struct iovec *out_sg)

+{

+    void *dest = buf->mem;

+

+    while (out_num) {

+        size_t onelen = out_sg->iov_len;

+        memcpy(dest, out_sg->iov_base, onelen);

+        dest += onelen;

+        out_sg++;

+        out_num--;

+    }

+}

+

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

 static void *fv_queue_thread(void *opaque)

 {

     struct fv_QueueInfo *qi = opaque;

+    struct VuDev *dev = &qi->virtio_dev->dev;

+    struct VuVirtq *q = vu_get_queue(dev, qi->qidx);

+    struct fuse_session *se = qi->virtio_dev->se;

+    struct fuse_chan ch;

+    struct fuse_buf fbuf;

+

+    fbuf.mem = NULL;

+    fbuf.flags = 0;

+

+    fuse_mutex_init(&ch.lock);

+    ch.fd = (int)0xdaff0d111;

+    ch.qi = qi;

+

     fuse_log(FUSE_LOG_INFO, "%s: Start for queue %d kick_fd %d\n", __func__,

              qi->qidx, qi->kick_fd);

     while (1) {

@@ -141,11 +174,71 @@ static void *fv_queue_thread(void *opaque)

             fuse_log(FUSE_LOG_ERR, "Eventfd_read for queue: %m\n");

             break;

         }

-        if (qi->virtio_dev->se->debug) {

-            fprintf(stderr, "%s: Queue %d gave evalue: %zx\n", __func__,

-                    qi->qidx, (size_t)evalue);

+        /* out is from guest, in is too guest */

+        unsigned int in_bytes, out_bytes;

+        vu_queue_get_avail_bytes(dev, q, &in_bytes, &out_bytes, ~0, ~0);

+

+        fuse_log(FUSE_LOG_DEBUG,

+                 "%s: Queue %d gave evalue: %zx available: in: %u out: %u\n",

+                 __func__, qi->qidx, (size_t)evalue, in_bytes, out_bytes);

+

+        while (1) {

+            /*

+             * An element contains one request and the space to send our

+             * response They're spread over multiple descriptors in a

+             * scatter/gather set and we can't trust the guest to keep them

+             * still; so copy in/out.

+             */

+            VuVirtqElement *elem = vu_queue_pop(dev, q, sizeof(VuVirtqElement));

+            if (!elem) {

+                break;

+            }

+

+            if (!fbuf.mem) {

+                fbuf.mem = malloc(se->bufsize);

+                assert(fbuf.mem);

+                assert(se->bufsize > sizeof(struct fuse_in_header));

+            }

+            /* The 'out' part of the elem is from qemu */

+            unsigned int out_num = elem->out_num;

+            struct iovec *out_sg = elem->out_sg;

+            size_t out_len = iov_size(out_sg, out_num);

+            fuse_log(FUSE_LOG_DEBUG,

+                     "%s: elem %d: with %d out desc of length %zd\n", __func__,

+                     elem->index, out_num, out_len);

+

+            /*

+             * The elem should contain a 'fuse_in_header' (in to fuse)

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

+             */

+            if (out_len < sizeof(struct fuse_in_header)) {

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

+                         __func__, elem->index);

+                assert(0); /* TODO */

+            }

+            if (out_len > se->bufsize) {

+                fuse_log(FUSE_LOG_ERR, "%s: elem %d too large for buffer\n",

+                         __func__, elem->index);

+                assert(0); /* TODO */

+            }

+            copy_from_iov(&fbuf, out_num, out_sg);

+            fbuf.size = out_len;

+

+            /* 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);

+

+            free(elem);

+            elem = NULL;

         }

     }

+    pthread_mutex_destroy(&ch.lock);

+    free(fbuf.mem);

     return NULL;

 }