Re: [Qemu-devel] [PATCH v4 08/29] libvhost-user: Open userfaultfd

[Marc-André Lureau]

On Thu, Mar 8, 2018 at 8:57 PM, Dr. David Alan Gilbert (git)
<address@hidden> wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> Open a userfaultfd (on a postcopy_advise) and send it back in
> the reply to the qemu for it to monitor.
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>

Reviewed-by: Marc-André Lureau <address@hidden>


> ---
>  contrib/libvhost-user/libvhost-user.c | 45 
> +++++++++++++++++++++++++++++++----
>  contrib/libvhost-user/libvhost-user.h |  3 +++
>  2 files changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/contrib/libvhost-user/libvhost-user.c 
> b/contrib/libvhost-user/libvhost-user.c
> index eb0ab9338c..0b563fc5ae 100644
> --- a/contrib/libvhost-user/libvhost-user.c
> +++ b/contrib/libvhost-user/libvhost-user.c
> @@ -26,9 +26,20 @@
>  #include <sys/socket.h>
>  #include <sys/eventfd.h>
>  #include <sys/mman.h>
> +#include "qemu/compiler.h"
> +
> +#if defined(__linux__)
> +#include <sys/syscall.h>
> +#include <fcntl.h>
> +#include <sys/ioctl.h>
>  #include <linux/vhost.h>
>
> -#include "qemu/compiler.h"
> +#ifdef __NR_userfaultfd
> +#include <linux/userfaultfd.h>
> +#endif
> +
> +#endif
> +
>  #include "qemu/atomic.h"
>
>  #include "libvhost-user.h"
> @@ -888,11 +899,37 @@ vu_set_config(VuDev *dev, VhostUserMsg *vmsg)
>  static bool
>  vu_set_postcopy_advise(VuDev *dev, VhostUserMsg *vmsg)
>  {
> -    /* TODO: Open ufd, pass it back in the request
> -     * TODO: Add addresses
> -     */
> +    dev->postcopy_ufd = -1;
> +#ifdef UFFDIO_API
> +    struct uffdio_api api_struct;
> +
> +    dev->postcopy_ufd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
> +    /* TODO: Add addresses */
>      vmsg->payload.u64 = 0xcafe;
>      vmsg->size = sizeof(vmsg->payload.u64);
> +#endif
> +
> +    if (dev->postcopy_ufd == -1) {
> +        vu_panic(dev, "Userfaultfd not available: %s", strerror(errno));
> +        goto out;
> +    }
> +
> +#ifdef UFFDIO_API
> +    api_struct.api = UFFD_API;
> +    api_struct.features = 0;
> +    if (ioctl(dev->postcopy_ufd, UFFDIO_API, &api_struct)) {
> +        vu_panic(dev, "Failed UFFDIO_API: %s", strerror(errno));
> +        close(dev->postcopy_ufd);
> +        dev->postcopy_ufd = -1;
> +        goto out;
> +    }
> +    /* TODO: Stash feature flags somewhere */
> +#endif
> +
> +out:
> +    /* Return a ufd to the QEMU */
> +    vmsg->fd_num = 1;
> +    vmsg->fds[0] = dev->postcopy_ufd;
>      return true; /* = send a reply */
>  }
>
> diff --git a/contrib/libvhost-user/libvhost-user.h 
> b/contrib/libvhost-user/libvhost-user.h
> index 00d78a8810..074b7860f6 100644
> --- a/contrib/libvhost-user/libvhost-user.h
> +++ b/contrib/libvhost-user/libvhost-user.h
> @@ -282,6 +282,9 @@ struct VuDev {
>       * re-initialize */
>      vu_panic_cb panic;
>      const VuDevIface *iface;
> +
> +    /* Postcopy data */
> +    int postcopy_ufd;
>  };
>
>  typedef struct VuVirtqElement {
> --
> 2.14.3
>
>



-- 
Marc-André Lureau