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([2a01:e0a:280:24f0:9db0:474c:ff43:9f5c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4792b0d5e55sm65679855e9.2.2025.12.04.09.46.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Dec 2025 09:46:21 -0800 (PST) Message-ID: Date: Thu, 4 Dec 2025 18:46:21 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 6/8] tap: cpr support To: Ben Chaney , qemu-devel@nongnu.org Cc: Peter Xu , Fabiano Rosas , "Michael S. Tsirkin" , Stefano Garzarella , Jason Wang , Alex Williamson , Eric Blake , Markus Armbruster , Stefan Weil , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , Paolo Bonzini , Hamza Khan , Mark Kanda , Joshua Hunt , Max Tottenham , Steve Sistare References: <20251203-cpr-tap-v3-0-3c12e0a61f8e@akamai.com> <20251203-cpr-tap-v3-6-3c12e0a61f8e@akamai.com> From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= Content-Language: en-US, fr Autocrypt: addr=clg@redhat.com; keydata= xsFNBFu8o3UBEADP+oJVJaWm5vzZa/iLgpBAuzxSmNYhURZH+guITvSySk30YWfLYGBWQgeo 8NzNXBY3cH7JX3/a0jzmhDc0U61qFxVgrPqs1PQOjp7yRSFuDAnjtRqNvWkvlnRWLFq4+U5t yzYe4SFMjFb6Oc0xkQmaK2flmiJNnnxPttYwKBPd98WfXMmjwAv7QfwW+OL3VlTPADgzkcqj 53bfZ4VblAQrq6Ctbtu7JuUGAxSIL3XqeQlAwwLTfFGrmpY7MroE7n9Rl+hy/kuIrb/TO8n0 ZxYXvvhT7OmRKvbYuc5Jze6o7op/bJHlufY+AquYQ4dPxjPPVUT/DLiUYJ3oVBWFYNbzfOrV RxEwNuRbycttMiZWxgflsQoHF06q/2l4ttS3zsV4TDZudMq0TbCH/uJFPFsbHUN91qwwaN/+ gy1j7o6aWMz+Ib3O9dK2M/j/O/Ube95mdCqN4N/uSnDlca3YDEWrV9jO1mUS/ndOkjxa34ia 70FjwiSQAsyIwqbRO3CGmiOJqDa9qNvd2TJgAaS2WCw/TlBALjVQ7AyoPEoBPj31K74Wc4GS Rm+FSch32ei61yFu6ACdZ12i5Edt+To+hkElzjt6db/UgRUeKfzlMB7PodK7o8NBD8outJGS tsL2GRX24QvvBuusJdMiLGpNz3uqyqwzC5w0Fd34E6G94806fwARAQABzSJDw6lkcmljIExl IEdvYXRlciA8Y2xnQHJlZGhhdC5jb20+wsGRBBMBCAA7FiEEoPZlSPBIlev+awtgUaNDx8/7 7KEFAmTLlVECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgkQUaNDx8/77KG0eg// S0zIzTcxkrwJ/9XgdcvVTnXLVF9V4/tZPfB7sCp8rpDCEseU6O0TkOVFoGWM39sEMiQBSvyY lHrP7p7E/JYQNNLh441MfaX8RJ5Ul3btluLapm8oHp/vbHKV2IhLcpNCfAqaQKdfk8yazYhh EdxTBlzxPcu+78uE5fF4wusmtutK0JG0sAgq0mHFZX7qKG6LIbdLdaQalZ8CCFMKUhLptW71 xe+aNrn7hScBoOj2kTDRgf9CE7svmjGToJzUxgeh9mIkxAxTu7XU+8lmL28j2L5uNuDOq9vl hM30OT+pfHmyPLtLK8+GXfFDxjea5hZLF+2yolE/ATQFt9AmOmXC+YayrcO2ZvdnKExZS1o8 VUKpZgRnkwMUUReaF/mTauRQGLuS4lDcI4DrARPyLGNbvYlpmJWnGRWCDguQ/LBPpbG7djoy k3NlvoeA757c4DgCzggViqLm0Bae320qEc6z9o0X0ePqSU2f7vcuWN49Uhox5kM5L86DzjEQ RHXndoJkeL8LmHx8DM+kx4aZt0zVfCHwmKTkSTQoAQakLpLte7tWXIio9ZKhUGPv/eHxXEoS 0rOOAZ6np1U/xNR82QbF9qr9TrTVI3GtVe7Vxmff+qoSAxJiZQCo5kt0YlWwti2fFI4xvkOi V7lyhOA3+/3oRKpZYQ86Frlo61HU3r6d9wzOwU0EW7yjdQEQALyDNNMw/08/fsyWEWjfqVhW pOOrX2h+z4q0lOHkjxi/FRIRLfXeZjFfNQNLSoL8j1y2rQOs1j1g+NV3K5hrZYYcMs0xhmrZ KXAHjjDx7FW3sG3jcGjFW5Xk4olTrZwFsZVUcP8XZlArLmkAX3UyrrXEWPSBJCXxDIW1hzwp bV/nVbo/K9XBptT/wPd+RPiOTIIRptjypGY+S23HYBDND3mtfTz/uY0Jytaio9GETj+fFis6 TxFjjbZNUxKpwftu/4RimZ7qL+uM1rG1lLWc9SPtFxRQ8uLvLOUFB1AqHixBcx7LIXSKZEFU CSLB2AE4wXQkJbApye48qnZ09zc929df5gU6hjgqV9Gk1rIfHxvTsYltA1jWalySEScmr0iS YBZjw8Nbd7SxeomAxzBv2l1Fk8fPzR7M616dtb3Z3HLjyvwAwxtfGD7VnvINPbzyibbe9c6g LxYCr23c2Ry0UfFXh6UKD83d5ybqnXrEJ5n/t1+TLGCYGzF2erVYGkQrReJe8Mld3iGVldB7 JhuAU1+d88NS3aBpNF6TbGXqlXGF6Yua6n1cOY2Yb4lO/mDKgjXd3aviqlwVlodC8AwI0Sdu jWryzL5/AGEU2sIDQCHuv1QgzmKwhE58d475KdVX/3Vt5I9kTXpvEpfW18TjlFkdHGESM/Jx IqVsqvhAJkalABEBAAHCwV8EGAECAAkFAlu8o3UCGwwACgkQUaNDx8/77KEhwg//WqVopd5k 8hQb9VVdk6RQOCTfo6wHhEqgjbXQGlaxKHoXywEQBi8eULbeMQf5l4+tHJWBxswQ93IHBQjK yKyNr4FXseUI5O20XVNYDJZUrhA4yn0e/Af0IX25d94HXQ5sMTWr1qlSK6Zu79lbH3R57w9j hQm9emQEp785ui3A5U2Lqp6nWYWXz0eUZ0Tad2zC71Gg9VazU9MXyWn749s0nXbVLcLS0yop s302Gf3ZmtgfXTX/W+M25hiVRRKCH88yr6it+OMJBUndQVAA/fE9hYom6t/zqA248j0QAV/p LHH3hSirE1mv+7jpQnhMvatrwUpeXrOiEw1nHzWCqOJUZ4SY+HmGFW0YirWV2mYKoaGO2YBU wYF7O9TI3GEEgRMBIRT98fHa0NPwtlTktVISl73LpgVscdW8yg9Gc82oe8FzU1uHjU8b10lU XOMHpqDDEV9//r4ZhkKZ9C4O+YZcTFu+mvAY3GlqivBNkmYsHYSlFsbxc37E1HpTEaSWsGfA HQoPn9qrDJgsgcbBVc1gkUT6hnxShKPp4PlsZVMNjvPAnr5TEBgHkk54HQRhhwcYv1T2QumQ izDiU6iOrUzBThaMhZO3i927SG2DwWDVzZltKrCMD1aMPvb3NU8FOYRhNmIFR3fcalYr+9gD uVKe8BVz4atMOoktmt0GWTOC8P4= In-Reply-To: <20251203-cpr-tap-v3-6-3c12e0a61f8e@akamai.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 12/3/25 19:51, Ben Chaney wrote: > From: Steve Sistare > > Provide the cpr=on option to preserve TAP and vhost descriptors during > cpr-transfer, so the management layer does not need to create a new > device for the target. > > Save all tap fd's in canonical order, leveraging the index argument of > cpr_save_fd. For the i'th queue, the tap device fd is saved at index 2*i, > and the vhostfd (if any) at index 2*i+1. > > tap and vhost fd's are passed by name to the monitor when a NIC is hot > plugged, but the name is not known to qemu after cpr. Allow the manager > to pass -1 for the fd "name" in the new qemu args to indicate that QEMU > should search for a saved value. Example: > > -netdev tap,id=hostnet2,fds=-1:-1,vhostfds=-1:-1,cpr=on > > Signed-off-by: Steve Sistare > Signed-off-by: Ben Chaney > --- > hw/vfio/device.c | 2 +- > include/migration/cpr.h | 2 +- > migration/cpr.c | 11 ++++---- > net/tap.c | 73 +++++++++++++++++++++++++++++++++++++++---------- > qapi/net.json | 5 +++- > 5 files changed, 70 insertions(+), 23 deletions(-) > > diff --git a/hw/vfio/device.c b/hw/vfio/device.c > index 76869828fc..73e622f7b5 100644 > --- a/hw/vfio/device.c > +++ b/hw/vfio/device.c > @@ -362,7 +362,7 @@ void vfio_device_free_name(VFIODevice *vbasedev) > > void vfio_device_set_fd(VFIODevice *vbasedev, const char *str, Error **errp) > { > - vbasedev->fd = cpr_get_fd_param(vbasedev->dev->id, str, 0, errp); > + vbasedev->fd = cpr_get_fd_param(vbasedev->dev->id, str, 0, true, errp); This looks weird to me. This calls a cpr* routine with a 'cpr' bool argument that toggles CPR on or off. It looks a bit hacky. Could you clarify the intention? C. > } > > static VFIODeviceIOOps vfio_device_io_ops_ioctl; > diff --git a/include/migration/cpr.h b/include/migration/cpr.h > index d585fadc5b..68424b4b03 100644 > --- a/include/migration/cpr.h > +++ b/include/migration/cpr.h > @@ -48,7 +48,7 @@ void cpr_state_close(void); > struct QIOChannel *cpr_state_ioc(void); > > bool cpr_incoming_needed(void *opaque); > -int cpr_get_fd_param(const char *name, const char *fdname, int index, > +int cpr_get_fd_param(const char *name, const char *fdname, int index, bool cpr, > Error **errp); > > QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp); > diff --git a/migration/cpr.c b/migration/cpr.c > index c0bf93a7ba..19bd56339d 100644 > --- a/migration/cpr.c > +++ b/migration/cpr.c > @@ -316,6 +316,7 @@ bool cpr_incoming_needed(void *opaque) > * @name: CPR name for the descriptor > * @fdname: An integer-valued string, or a name passed to a getfd command > * @index: CPR index of the descriptor > + * @cpr: use cpr > * @errp: returned error message > * > * If CPR is not being performed, then use @fdname to find the fd. > @@ -325,22 +326,22 @@ bool cpr_incoming_needed(void *opaque) > * On success returns the fd value, else returns -1. > */ > int cpr_get_fd_param(const char *name, const char *fdname, int index, > - Error **errp) > + bool cpr, Error **errp) > { > ERRP_GUARD(); > int fd; > > - if (cpr_is_incoming()) { > + if (cpr && cpr_is_incoming()) { > fd = cpr_find_fd(name, index); > if (fd < 0) { > error_setg(errp, "cannot find saved value for fd %s", fdname); > } > } else { > fd = monitor_fd_param(monitor_cur(), fdname, errp); > - if (fd >= 0) { > - cpr_save_fd(name, index, fd); > - } else { > + if (fd < 0) { > error_prepend(errp, "Could not parse object fd %s:", fdname); > + } else if (cpr) { > + cpr_save_fd(name, index, fd); > } > } > return fd; > diff --git a/net/tap.c b/net/tap.c > index 9d480574c3..79e29addd1 100644 > --- a/net/tap.c > +++ b/net/tap.c > @@ -35,6 +35,7 @@ > #include "net/eth.h" > #include "net/net.h" > #include "clients.h" > +#include "migration/cpr.h" > #include "monitor/monitor.h" > #include "system/system.h" > #include "qapi/error.h" > @@ -80,6 +81,7 @@ typedef struct TAPState { > bool has_uso; > bool has_tunnel; > bool enabled; > + bool cpr; > VHostNetState *vhost_net; > unsigned host_vnet_hdr_len; > Notifier exit; > @@ -323,6 +325,9 @@ static void tap_cleanup(NetClientState *nc) > { > TAPState *s = DO_UPCAST(TAPState, nc, nc); > > + if (s->cpr) { > + cpr_delete_fd_all(nc->name); > + } > if (s->vhost_net) { > vhost_net_cleanup(s->vhost_net); > g_free(s->vhost_net); > @@ -690,18 +695,24 @@ static int net_tap_init(const NetdevTapOptions *tap, int *vnet_hdr, > return fd; > } > > +/* CPR fd's for each queue are saved at these indices */ > +#define TAP_FD_INDEX(queue) (2 * (queue) + 0) > +#define TAP_VHOSTFD_INDEX(queue) (2 * (queue) + 1) > + > #define MAX_TAP_QUEUES 1024 > > static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer, > const char *model, const char *name, > const char *ifname, const char *script, > const char *downscript, const char *vhostfdname, > - int vnet_hdr, int fd, Error **errp) > + int vnet_hdr, int fd, int index, Error **errp) > { > Error *err = NULL; > TAPState *s = net_tap_fd_init(peer, model, name, fd, vnet_hdr); > + bool cpr = tap->has_cpr ? tap->cpr : false; > int vhostfd; > > + s->cpr = cpr; > tap_set_sndbuf(s->fd, tap, &err); > if (err) { > error_propagate(errp, err); > @@ -736,7 +747,7 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer, > } > > if (vhostfdname) { > - vhostfd = monitor_fd_param(monitor_cur(), vhostfdname, &err); > + vhostfd = cpr_get_fd_param(name, vhostfdname, index, cpr, &err); > if (vhostfd == -1) { > error_propagate(errp, err); > goto failed; > @@ -745,13 +756,22 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer, > goto failed; > } > } else { > - vhostfd = open("/dev/vhost-net", O_RDWR); > + vhostfd = cpr ? cpr_find_fd(name, index) : -1; > + if (vhostfd < 0) { > + vhostfd = open("/dev/vhost-net", O_RDWR); > + if (cpr && vhostfd >= 0) { > + cpr_save_fd(name, index, vhostfd); > + } > + } > if (vhostfd < 0) { > error_setg_errno(errp, errno, > "tap: open vhost char device failed"); > goto failed; > } > if (!qemu_set_blocking(vhostfd, false, errp)) { > + if (!cpr) { > + close(vhostfd); > + } > goto failed; > } > } > @@ -777,6 +797,9 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer, > return; > > failed: > + if (cpr) { > + cpr_delete_fd_all(name); > + } > qemu_del_net_client(&s->nc); > } > > @@ -809,7 +832,8 @@ static int get_fds(char *str, char *fds[], int max) > int net_init_tap(const Netdev *netdev, const char *name, > NetClientState *peer, Error **errp) > { > - const NetdevTapOptions *tap; > + const NetdevTapOptions *tap = &netdev->u.tap; > + bool cpr = tap->has_cpr ? tap->cpr : false; > int fd, vnet_hdr = 0, i = 0, queues; > /* for the no-fd, no-helper case */ > const char *script; > @@ -845,7 +869,7 @@ int net_init_tap(const Netdev *netdev, const char *name, > goto out; > } > > - fd = monitor_fd_param(monitor_cur(), tap->fd, errp); > + fd = cpr_get_fd_param(name, tap->fd, TAP_FD_INDEX(0), cpr, errp); > if (fd == -1) { > ret = -1; > goto out; > @@ -866,13 +890,14 @@ int net_init_tap(const Netdev *netdev, const char *name, > > net_init_tap_one(tap, peer, "tap", name, NULL, > script, downscript, > - vhostfdname, vnet_hdr, fd, &err); > + vhostfdname, vnet_hdr, fd, TAP_VHOSTFD_INDEX(0), &err); > if (err) { > error_propagate(errp, err); > close(fd); > ret = -1; > goto out; > } > + > } else if (tap->fds) { > char **fds; > char **vhost_fds; > @@ -903,7 +928,7 @@ int net_init_tap(const Netdev *netdev, const char *name, > } > > for (i = 0; i < nfds; i++) { > - fd = monitor_fd_param(monitor_cur(), fds[i], errp); > + fd = cpr_get_fd_param(name, fds[i], TAP_FD_INDEX(i), cpr, errp); > if (fd == -1) { > ret = -1; > goto free_fail; > @@ -930,7 +955,7 @@ int net_init_tap(const Netdev *netdev, const char *name, > net_init_tap_one(tap, peer, "tap", name, ifname, > script, downscript, > tap->vhostfds ? vhost_fds[i] : NULL, > - vnet_hdr, fd, &err); > + vnet_hdr, fd, TAP_VHOSTFD_INDEX(i), &err); > if (err) { > error_propagate(errp, err); > ret = -1; > @@ -958,9 +983,15 @@ free_fail: > goto out; > } > > - fd = net_bridge_run_helper(tap->helper, > - tap->br ?: DEFAULT_BRIDGE_INTERFACE, > - errp); > + fd = cpr ? cpr_find_fd(name, TAP_FD_INDEX(0)) : -1; > + if (fd < 0) { > + fd = net_bridge_run_helper(tap->helper, > + tap->br ?: DEFAULT_BRIDGE_INTERFACE, > + errp); > + if (cpr && fd >= 0) { > + cpr_save_fd(name, TAP_FD_INDEX(0), fd); > + } > + } > if (fd == -1) { > ret = -1; > goto out; > @@ -980,13 +1011,14 @@ free_fail: > > net_init_tap_one(tap, peer, "bridge", name, ifname, > script, downscript, vhostfdname, > - vnet_hdr, fd, &err); > + vnet_hdr, fd, TAP_VHOSTFD_INDEX(0), &err); > if (err) { > error_propagate(errp, err); > close(fd); > ret = -1; > goto out; > } > + > } else { > g_autofree char *default_script = NULL; > g_autofree char *default_downscript = NULL; > @@ -1011,8 +1043,14 @@ free_fail: > } > > for (i = 0; i < queues; i++) { > - fd = net_tap_init(tap, &vnet_hdr, i >= 1 ? "no" : script, > - ifname, sizeof ifname, queues > 1, errp); > + fd = cpr ? cpr_find_fd(name, TAP_FD_INDEX(i)) : -1; > + if (fd < 0) { > + fd = net_tap_init(tap, &vnet_hdr, i >= 1 ? "no" : script, > + ifname, sizeof ifname, queues > 1, errp); > + if (cpr && fd >= 0) { > + cpr_save_fd(name, TAP_FD_INDEX(i), fd); > + } > + } > if (fd == -1) { > ret = -1; > goto out; > @@ -1030,7 +1068,9 @@ free_fail: > net_init_tap_one(tap, peer, "tap", name, ifname, > i >= 1 ? "no" : script, > i >= 1 ? "no" : downscript, > - vhostfdname, vnet_hdr, fd, &err); > + vhostfdname, vnet_hdr, > + fd, TAP_VHOSTFD_INDEX(i), > + &err); > if (err) { > error_propagate(errp, err); > close(fd); > @@ -1041,6 +1081,9 @@ free_fail: > } > > out: > + if (ret && cpr) { > + cpr_delete_fd_all(name); > + } > return ret; > } > > diff --git a/qapi/net.json b/qapi/net.json > index 118bd34965..264213b5d9 100644 > --- a/qapi/net.json > +++ b/qapi/net.json > @@ -355,6 +355,8 @@ > # @poll-us: maximum number of microseconds that could be spent on busy > # polling for tap (since 2.7) > # > +# @cpr: preserve fds and vhostfds during cpr-transfer. > +# > # Since: 1.2 > ## > { 'struct': 'NetdevTapOptions', > @@ -373,7 +375,8 @@ > '*vhostfds': 'str', > '*vhostforce': 'bool', > '*queues': 'uint32', > - '*poll-us': 'uint32'} } > + '*poll-us': 'uint32', > + '*cpr': 'bool'} } > > ## > # @NetdevSocketOptions: >