From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36746) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dmZuq-0006O4-LF for qemu-devel@nongnu.org; Tue, 29 Aug 2017 02:22:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dmZum-0000Sj-Ie for qemu-devel@nongnu.org; Tue, 29 Aug 2017 02:22:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55654) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dmZum-0000SS-8l for qemu-devel@nongnu.org; Tue, 29 Aug 2017 02:22:20 -0400 Date: Tue, 29 Aug 2017 14:22:07 +0800 From: Peter Xu Message-ID: <20170829062207.GV14174@pxdev.xzpeter.org> References: <20170824192730.8440-1-dgilbert@redhat.com> <20170824192730.8440-9-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170824192730.8440-9-dgilbert@redhat.com> Subject: Re: [Qemu-devel] [RFC v2 08/32] postcopy: Add vhost-user flag for postcopy and check it List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" Cc: qemu-devel@nongnu.org, maxime.coquelin@redhat.com, a.perevalov@samsung.com, mst@redhat.com, marcandre.lureau@redhat.com, quintela@redhat.com, lvivier@redhat.com, aarcange@redhat.com, felipe@nutanix.com On Thu, Aug 24, 2017 at 08:27:06PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > Add a vhost feature flag for postcopy support, and > use the postcopy notifier to check it before allowing postcopy. > > Signed-off-by: Dr. David Alan Gilbert > --- > contrib/libvhost-user/libvhost-user.h | 1 + > docs/interop/vhost-user.txt | 10 +++++++++ > hw/virtio/vhost-user.c | 40 ++++++++++++++++++++++++++++++++++- > 3 files changed, 50 insertions(+), 1 deletion(-) > > diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h > index acd019876d..95d0d34a28 100644 > --- a/contrib/libvhost-user/libvhost-user.h > +++ b/contrib/libvhost-user/libvhost-user.h > @@ -34,6 +34,7 @@ enum VhostUserProtocolFeature { > VHOST_USER_PROTOCOL_F_MQ = 0, > VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1, > VHOST_USER_PROTOCOL_F_RARP = 2, > + VHOST_USER_PROTOCOL_F_PAGEFAULT = 7, > > VHOST_USER_PROTOCOL_F_MAX > }; > diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt > index 954771d0d8..a279560eb0 100644 > --- a/docs/interop/vhost-user.txt > +++ b/docs/interop/vhost-user.txt > @@ -273,6 +273,15 @@ Once the source has finished migration, rings will be stopped by > the source. No further update must be done before rings are > restarted. > > +In postcopy migration the slave is started before all the memory has been > +received from the source host, and care must be taken to avoid accessing pages > +that have yet to be received. The slave opens a 'userfault'-fd and registers > +the memory with it; this fd is then passed back over to the master. > +The master services requests on the userfaultfd for pages that are accessed > +and when the page is available it performs WAKE ioctl's on the userfaultfd > +to wake the stalled slave. The client indicates support for this via the > +VHOST_USER_PROTOCOL_F_PAGEFAULT feature. > + > IOMMU support > ------------- > > @@ -327,6 +336,7 @@ Protocol features > #define VHOST_USER_PROTOCOL_F_MTU 4 > #define VHOST_USER_PROTOCOL_F_SLAVE_REQ 5 > #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6 > +#define VHOST_USER_PROTOCOL_F_PAGEFAULT 7 > > Master message types > -------------------- > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index 093675ed98..c51bbd1296 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -17,6 +17,8 @@ > #include "sysemu/kvm.h" > #include "qemu/error-report.h" > #include "qemu/sockets.h" > +#include "migration/migration.h" > +#include "migration/postcopy-ram.h" > > #include > #include > @@ -34,7 +36,7 @@ enum VhostUserProtocolFeature { > VHOST_USER_PROTOCOL_F_NET_MTU = 4, > VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5, > VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6, > - > + VHOST_USER_PROTOCOL_F_PAGEFAULT = 7, > VHOST_USER_PROTOCOL_F_MAX > }; > > @@ -123,8 +125,10 @@ static VhostUserMsg m __attribute__ ((unused)); > #define VHOST_USER_VERSION (0x1) > > struct vhost_user { > + struct vhost_dev *dev; > CharBackend *chr; > int slave_fd; > + NotifierWithReturn postcopy_notifier; > }; > > static bool ioeventfd_enabled(void) > @@ -720,6 +724,33 @@ out: > return ret; > } > > +static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier, > + void *opaque) > +{ > + struct PostcopyNotifyData *pnd = opaque; > + struct vhost_user *u = container_of(notifier, struct vhost_user, > + postcopy_notifier); > + struct vhost_dev *dev = u->dev; > + > + switch (pnd->reason) { > + case POSTCOPY_NOTIFY_PROBE: > + if (!virtio_has_feature(dev->protocol_features, > + VHOST_USER_PROTOCOL_F_PAGEFAULT)) { > + /* TODO: Get the device name into this error somehow */ > + error_setg(pnd->errp, > + "vhost-user backend not capable of postcopy"); > + return -ENOENT; > + } > + break; > + > + default: > + /* We ignore notifications we don't know */ > + break; > + } > + > + return 0; > +} > + > static int vhost_user_init(struct vhost_dev *dev, void *opaque) > { > uint64_t features, protocol_features; > @@ -731,6 +762,7 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque) > u = g_new0(struct vhost_user, 1); > u->chr = opaque; > u->slave_fd = -1; > + u->dev = dev; > dev->opaque = u; > > err = vhost_user_get_features(dev, &features); > @@ -787,6 +819,9 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque) > return err; > } > > + u->postcopy_notifier.notify = vhost_user_postcopy_notifier; > + postcopy_add_notifier(&u->postcopy_notifier); > + > return 0; > } > > @@ -797,6 +832,9 @@ static int vhost_user_cleanup(struct vhost_dev *dev) > assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER); > > u = dev->opaque; > + if (u->postcopy_notifier.notify) { Detecting init using the notify hook is slightly strange here for me... If so, not sure whether we also need: u->postcopy_notifier.notify = NULL; Or I'm not sure whether a 2nd call to vhost_user_cleanup() can be dangerous since postcopy_remove_notifier() will be called twice. Besides that, the patch looks good to me. Thanks, > + postcopy_remove_notifier(&u->postcopy_notifier); > + } > if (u->slave_fd >= 0) { > qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL); > close(u->slave_fd); > -- > 2.13.5 > -- Peter Xu