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vhost-user: Convert slave channel to QIOChannelSocket 

The slave channel is implemented with socketpair() : QEMU creates
the pair, passes one of the socket to virtiofsd and monitors the
other one with the main event loop using qemu_set_fd_handler().

In order to fix a potential deadlock between QEMU and a vhost-user
external process (e.g. virtiofsd with DAX), we want to be able to
monitor and service the slave channel while handling vhost-user
requests.

Prepare ground for this by converting the slave channel to be a
QIOChannelSocket. This will make monitoring of the slave channel
as simple as calling qio_channel_add_watch_source(). Since the
connection is already established between the two sockets, only
incoming I/O (G_IO_IN) and disconnect (G_IO_HUP) need to be
serviced.

This also allows to get rid of the ancillary data parsing since
QIOChannelSocket can do this for us. Note that the MSG_CTRUNC
check is dropped on the way because QIOChannelSocket ignores this
case. This isn't a problem since slave_read() provisions space for
8 file descriptors, but affected vhost-user slave protocol messages
generally only convey one. If for some reason a buggy implementation
passes more file descriptors, no need to break the connection, just
like we don't break it if some other type of ancillary data is
received : this isn't explicitely violating the protocol per-se so
it seems better to ignore it.

The current code errors out on short reads and writes. Use the
qio_channel_*_all() variants to address this on the way.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20210312092212.782255-5-groug@kaod.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Greg Kurz 2021-03-12 10:22:09 +01:00 committed by Michael S. Tsirkin
parent de62e49460
commit 57dc02173c
1 changed files with 39 additions and 60 deletions
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99
hw/virtio/vhost-user.c
View File

@ -16,6 +16,7 @@
#include "hw/virtio/virtio.h"
#include "hw/virtio/virtio-net.h"
#include "chardev/char-fe.h"
#include "io/channel-socket.h"
#include "sysemu/kvm.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
@ -237,7 +238,8 @@ struct vhost_user {
struct vhost_dev *dev;
/* Shared between vhost devs of the same virtio device */
VhostUserState *user;
int slave_fd;
QIOChannel *slave_ioc;
GSource *slave_src;
NotifierWithReturn postcopy_notifier;
struct PostCopyFD postcopy_fd;
uint64_t postcopy_client_bases[VHOST_USER_MAX_RAM_SLOTS];
@ -1394,61 +1396,37 @@ static int vhost_user_slave_handle_vring_host_notifier(struct vhost_dev *dev,
static void close_slave_channel(struct vhost_user *u)
{
qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL);
close(u->slave_fd);
u->slave_fd = -1;
g_source_destroy(u->slave_src);
g_source_unref(u->slave_src);
u->slave_src = NULL;
object_unref(OBJECT(u->slave_ioc));
u->slave_ioc = NULL;
}
static void slave_read(void *opaque)
static gboolean slave_read(QIOChannel *ioc, GIOCondition condition,
gpointer opaque)
{
struct vhost_dev *dev = opaque;
struct vhost_user *u = dev->opaque;
VhostUserHeader hdr = { 0, };
VhostUserPayload payload = { 0, };
int size, ret = 0;
Error *local_err = NULL;
gboolean rc = G_SOURCE_CONTINUE;
int ret = 0;
struct iovec iov;
struct msghdr msgh;
int fd[VHOST_USER_SLAVE_MAX_FDS];
char control[CMSG_SPACE(sizeof(fd))];
struct cmsghdr *cmsg;
int i, fdsize = 0;
memset(&msgh, 0, sizeof(msgh));
msgh.msg_iov = &iov;
msgh.msg_iovlen = 1;
msgh.msg_control = control;
msgh.msg_controllen = sizeof(control);
memset(fd, -1, sizeof(fd));
g_autofree int *fd = NULL;
size_t fdsize = 0;
int i;
/* Read header */
iov.iov_base = &hdr;
iov.iov_len = VHOST_USER_HDR_SIZE;
do {
size = recvmsg(u->slave_fd, &msgh, 0);
} while (size < 0 && errno == EINTR);
if (size != VHOST_USER_HDR_SIZE) {
error_report("Failed to read from slave.");
if (qio_channel_readv_full_all(ioc, &iov, 1, &fd, &fdsize, &local_err)) {
error_report_err(local_err);
goto err;
}
if (msgh.msg_flags & MSG_CTRUNC) {
error_report("Truncated message.");
goto err;
}
for (cmsg = CMSG_FIRSTHDR(&msgh); cmsg != NULL;
cmsg = CMSG_NXTHDR(&msgh, cmsg)) {
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_RIGHTS) {
fdsize = cmsg->cmsg_len - CMSG_LEN(0);
memcpy(fd, CMSG_DATA(cmsg), fdsize);
break;
}
}
if (hdr.size > VHOST_USER_PAYLOAD_SIZE) {
error_report("Failed to read msg header."
" Size %d exceeds the maximum %zu.", hdr.size,
@ -1457,12 +1435,8 @@ static void slave_read(void *opaque)
}
/* Read payload */
do {
size = read(u->slave_fd, &payload, hdr.size);
} while (size < 0 && errno == EINTR);
if (size != hdr.size) {
error_report("Failed to read payload from slave.");
if (qio_channel_read_all(ioc, (char *) &payload, hdr.size, &local_err)) {
error_report_err(local_err);
goto err;
}
@ -1475,7 +1449,7 @@ static void slave_read(void *opaque)
break;
case VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG:
ret = vhost_user_slave_handle_vring_host_notifier(dev, &payload.area,
fd[0]);
fd ? fd[0] : -1);
break;
default:
error_report("Received unexpected msg type: %d.", hdr.request);
@ -1501,12 +1475,8 @@ static void slave_read(void *opaque)
iovec[1].iov_base = &payload;
iovec[1].iov_len = hdr.size;
do {
size = writev(u->slave_fd, iovec, ARRAY_SIZE(iovec));
} while (size < 0 && errno == EINTR);
if (size != VHOST_USER_HDR_SIZE + hdr.size) {
error_report("Failed to send msg reply to slave.");
if (qio_channel_writev_all(ioc, iovec, ARRAY_SIZE(iovec), &local_err)) {
error_report_err(local_err);
goto err;
}
}
@ -1515,14 +1485,15 @@ static void slave_read(void *opaque)
err:
close_slave_channel(u);
rc = G_SOURCE_REMOVE;
fdcleanup:
for (i = 0; i < fdsize; i++) {
if (fd[i] != -1) {
if (fd) {
for (i = 0; i < fdsize; i++) {
close(fd[i]);
}
}
return;
return rc;
}
static int vhost_setup_slave_channel(struct vhost_dev *dev)
@ -1535,6 +1506,8 @@ static int vhost_setup_slave_channel(struct vhost_dev *dev)
int sv[2], ret = 0;
bool reply_supported = virtio_has_feature(dev->protocol_features,
VHOST_USER_PROTOCOL_F_REPLY_ACK);
Error *local_err = NULL;
QIOChannel *ioc;
if (!virtio_has_feature(dev->protocol_features,
VHOST_USER_PROTOCOL_F_SLAVE_REQ)) {
@ -1546,8 +1519,15 @@ static int vhost_setup_slave_channel(struct vhost_dev *dev)
return -1;
}
u->slave_fd = sv[0];
qemu_set_fd_handler(u->slave_fd, slave_read, NULL, dev);
ioc = QIO_CHANNEL(qio_channel_socket_new_fd(sv[0], &local_err));
if (!ioc) {
error_report_err(local_err);
return -1;
}
u->slave_ioc = ioc;
u->slave_src = qio_channel_add_watch_source(u->slave_ioc,
G_IO_IN | G_IO_HUP,
slave_read, dev, NULL, NULL);
if (reply_supported) {
msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
@ -1802,7 +1782,6 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
u = g_new0(struct vhost_user, 1);
u->user = opaque;
u->slave_fd = -1;
u->dev = dev;
dev->opaque = u;
@ -1917,7 +1896,7 @@ static int vhost_user_backend_cleanup(struct vhost_dev *dev)
close(u->postcopy_fd.fd);
u->postcopy_fd.handler = NULL;
}
if (u->slave_fd >= 0) {
if (u->slave_ioc) {
close_slave_channel(u);
}
g_free(u->region_rb);