On Fri, Sep 15, 2023 at 12:25:25PM +0200, Hanna Czenczek wrote: > RFC: > https://lists.nongnu.org/archive/html/qemu-devel/2023-03/msg04263.html > > v1: > https://lists.nongnu.org/archive/html/qemu-devel/2023-04/msg01575.html > > v2: > https://lists.nongnu.org/archive/html/qemu-devel/2023-07/msg02604.html > > Hi, > > I’ve decided not to work on vhost-user SUSPEND/RESUME for now – it is > not technically required for virtio-fs migration, which is the actual > priority for me now. While we do want to have SUSPEND/RESUME at some > point, the only practically existing reason for it is to be able to > implement vhost-level resetting in virtiofsd, but that is not related to > migration.
QEMU sends VHOST_USER_SET_STATUS 0 in vhost_dev_stop(). Are you assuming that virtiofs back-ends do not reset the device upon receiving this message? > So one of the changes in v3 is that it no longer depends on the > vhost-user SUSPEND/RESUME series, and describes the migration protocol > without the device being suspended at any point, but merely that the > vrings are stopped. > > Other changes include: > > - Patch 1: > - Rephrased a lot > - Added a description for the VHOST_USER_SET_DEVICE_STATE_FD > parameters > - Renamed VHOST_USER_PROTOCOL_F_MIGRATORY_STATE to > VHOST_USER_PROTOCOL_F_DEVICE_STATE > - enum variants changed in value due to dropping the SUSPEND/RESUME > dependency > > - Patch 2: > - Pulled in, was a stand-alone patch before > - Dropped a sentence about ring state before feature negotiations, as > the rings are not to be used during that period anyway > - Bit of rephrasing > > - Patch 3: > - Renamed “migratory state” to “device state” > - enum variants changed in value due to dropping the SUSPEND/RESUME > dependency > > - Patch 4: > - Changed `f` to @f (referencing parameter “f”) in comments > - Use g_autofree for the transfer buffer > - Note SUSPEND state as a future feature, not currently existing > - Wrap read() and write() in RETRY_ON_EINTR() > > - Patch 5: > - Renamed “migratory state” to “device state” > - (kept R-b still) > > > Hanna Czenczek (5): > vhost-user.rst: Migrating back-end-internal state > vhost-user.rst: Clarify enabling/disabling vrings > vhost-user: Interface for migration state transfer > vhost: Add high-level state save/load functions > vhost-user-fs: Implement internal migration > > docs/interop/vhost-user.rst | 188 ++++++++++++++++++++++- > include/hw/virtio/vhost-backend.h | 24 +++ > include/hw/virtio/vhost.h | 114 ++++++++++++++ > hw/virtio/vhost-user-fs.c | 101 ++++++++++++- > hw/virtio/vhost-user.c | 148 ++++++++++++++++++ > hw/virtio/vhost.c | 241 ++++++++++++++++++++++++++++++ > 6 files changed, 810 insertions(+), 6 deletions(-) > > -- > 2.41.0 >
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