Re: [dpdk-dev] [PATCH v4 11/19] vhost: introduce postcopy's advise message

[Maxime Coquelin]

On 10/08/2018 06:22 PM, Ilya Maximets wrote:

On 08.10.2018 18:25, Maxime Coquelin wrote:

This patch opens a userfaultfd and sends it back to Qemu's
VHOST_USER_POSTCOPY_ADVISE request.

Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
  lib/librte_vhost/vhost.h      |  2 ++
  lib/librte_vhost/vhost_user.c | 49 +++++++++++++++++++++++++++++++++++
  lib/librte_vhost/vhost_user.h |  3 ++-
  3 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 25ffd7614..21722d8a8 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -363,6 +363,8 @@ struct virtio_net {
        int                     slave_req_fd;
        rte_spinlock_t          slave_req_lock;

+ int postcopy_ufd;

+
        /*
         * Device id to identify a specific backend device.
         * It's set to -1 for the default software implementation.
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 20f38267d..3cdd2af28 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -24,13 +24,19 @@
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
  #include <sys/mman.h>
  #include <sys/types.h>
  #include <sys/stat.h>
+#include <sys/syscall.h>
  #include <assert.h>
  #ifdef RTE_LIBRTE_VHOST_NUMA
  #include <numaif.h>
  #endif
+#ifdef RTE_LIBRTE_VHOST_POSTCOPY
+#include <linux/userfaultfd.h>
+#endif

#include <rte_common.h>

  #include <rte_malloc.h>
@@ -69,6 +75,7 @@ static const char *vhost_message_str[VHOST_USER_MAX] = {
        [VHOST_USER_IOTLB_MSG]  = "VHOST_USER_IOTLB_MSG",
        [VHOST_USER_CRYPTO_CREATE_SESS] = "VHOST_USER_CRYPTO_CREATE_SESS",
        [VHOST_USER_CRYPTO_CLOSE_SESS] = "VHOST_USER_CRYPTO_CLOSE_SESS",
+       [VHOST_USER_POSTCOPY_ADVISE]  = "VHOST_USER_POSTCOPY_ADVISE",
  };

/* The possible results of a message handling function */

@@ -130,6 +137,11 @@ vhost_backend_cleanup(struct virtio_net *dev)
                close(dev->slave_req_fd);
                dev->slave_req_fd = -1;
        }
+
+       if (dev->postcopy_ufd >= 0) {
+               close(dev->postcopy_ufd);
+               dev->postcopy_ufd = -1;
+       }
  }

/*

@@ -1508,6 +1520,42 @@ vhost_user_iotlb_msg(struct virtio_net **pdev, struct 
VhostUserMsg *msg,
        return VH_RESULT_OK;
  }

+static int

+vhost_user_set_postcopy_advise(struct virtio_net **pdev,
+                       struct VhostUserMsg *msg,
+                       int main_fd __rte_unused)
+{
+       struct virtio_net *dev = *pdev;
+#ifdef RTE_LIBRTE_VHOST_POSTCOPY
+       struct uffdio_api api_struct;
+
+       dev->postcopy_ufd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+
+       if (dev->postcopy_ufd == -1) {
+               RTE_LOG(ERR, VHOST_CONFIG, "Userfaultfd not available: %s\n",
+                               strerror(errno));
+               return VH_RESULT_ERR;
+       }
+       api_struct.api = UFFD_API;
+       api_struct.features = 0;
+       if (ioctl(dev->postcopy_ufd, UFFDIO_API, &api_struct)) {
+               RTE_LOG(ERR, VHOST_CONFIG, "UFFDIO_API ioctl failure: %s\n",
+                               strerror(errno));
+               close(dev->postcopy_ufd);

Need to clear dev->postcopy_ufd value to avoid accidental closing of some
other fd on backend cleanup.

Good catch, it will be fixed in v5.

Thanks!
Maxime