* Peter Xu (pet...@redhat.com) wrote: > On Thu, Aug 24, 2017 at 08:27:09PM +0100, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > > > 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 <dgilb...@redhat.com> > > --- > > contrib/libvhost-user/libvhost-user.c | 26 +++++++++++++++++++++++--- > > contrib/libvhost-user/libvhost-user.h | 3 +++ > > 2 files changed, 26 insertions(+), 3 deletions(-) > > > > diff --git a/contrib/libvhost-user/libvhost-user.c > > b/contrib/libvhost-user/libvhost-user.c > > index 47884c0a15..f9b5b12b28 100644 > > --- a/contrib/libvhost-user/libvhost-user.c > > +++ b/contrib/libvhost-user/libvhost-user.c > > @@ -15,6 +15,7 @@ > > > > #include <qemu/osdep.h> > > #include <sys/eventfd.h> > > +#include <sys/syscall.h> > > #include <linux/vhost.h> > > > > #include "qemu/atomic.h" > > @@ -773,11 +774,30 @@ 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)); > > + goto out; > > We got error but still goto out? I feel like we should reply with > some kind of error code when any error happens.
See that the out: code returns the dev->postcopy_ufd to qemu and in this case it's -1 so it is already flagged as an error. > > + } > > + 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; > > Same here. And there we explicitly set dev->postcopy_ufd = -1 before going to out so it's sent as the error value. > > + } > > + /* TODO: Stash feature flags somewhere */ > > +out: > > + /* Return a ufd to the QEMU */ > > + vmsg->fd_num = 1; > > + vmsg->fds[0] = dev->postcopy_ufd; ^^^ see that's where the -1's end up. > > return true; /* = send a reply */ > > } Dave > > > > diff --git a/contrib/libvhost-user/libvhost-user.h > > b/contrib/libvhost-user/libvhost-user.h > > index 3987ce643d..3e8efdd919 100644 > > --- a/contrib/libvhost-user/libvhost-user.h > > +++ b/contrib/libvhost-user/libvhost-user.h > > @@ -234,6 +234,9 @@ struct VuDev { > > * re-initialize */ > > vu_panic_cb panic; > > const VuDevIface *iface; > > + > > + /* Postcopy data */ > > + int postcopy_ufd; > > }; > > > > typedef struct VuVirtqElement { > > -- > > 2.13.5 > > > > -- > Peter Xu -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK