From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41296) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dZcI3-0006Nc-Rn for qemu-devel@nongnu.org; Mon, 24 Jul 2017 08:16:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dZcI0-0007nV-Ot for qemu-devel@nongnu.org; Mon, 24 Jul 2017 08:16:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52960) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dZcI0-0007mM-FS for qemu-devel@nongnu.org; Mon, 24 Jul 2017 08:16:44 -0400 References: <20170628190047.26159-1-dgilbert@redhat.com> <20170628190047.26159-11-dgilbert@redhat.com> From: Maxime Coquelin Message-ID: Date: Mon, 24 Jul 2017 14:10:34 +0200 MIME-Version: 1.0 In-Reply-To: <20170628190047.26159-11-dgilbert@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC 10/29] vhub: Open userfaultfd List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, a.perevalov@samsung.com, marcandre.lureau@redhat.com, mst@redhat.com, quintela@redhat.com, peterx@redhat.com, lvivier@redhat.com, aarcange@redhat.com On 06/28/2017 09:00 PM, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > 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 > --- > contrib/libvhost-user/libvhost-user.c | 24 +++++++++++++++++++++--- > contrib/libvhost-user/libvhost-user.h | 3 +++ > 2 files changed, 24 insertions(+), 3 deletions(-) > > diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c > index e3a32755cf..62e97f6b84 100644 > --- a/contrib/libvhost-user/libvhost-user.c > +++ b/contrib/libvhost-user/libvhost-user.c > @@ -15,6 +15,7 @@ > > #include > #include > +#include > #include > > #include "qemu/atomic.h" > @@ -774,11 +775,28 @@ vu_set_vring_enable_exec(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 > - */ > + 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); > + > + if (dev->postcopy_ufd == -1) { > + vu_panic(dev, "Userfaultfd not available: %s", strerror(errno)); > + return false; I think we may want to reply something even in case of error. Indeed, if something goes wrong on backend side, Qemu will remain blocked waiting for the reply. > + } > + 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); > + return false; Ditto > + } > + /* TODO: Stash feature flags somewhere */ > + /* 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 8bb35582ea..3e65a962da 100644 > --- a/contrib/libvhost-user/libvhost-user.h > +++ b/contrib/libvhost-user/libvhost-user.h > @@ -231,6 +231,9 @@ struct VuDev { > * re-initialize */ > vu_panic_cb panic; > const VuDevIface *iface; > + > + /* Postcopy data */ > + int postcopy_ufd; > }; > > typedef struct VuVirtqElement { >