riscv/qemu - qemu - Gitea: Git with a cup of tea

Author	SHA1	Message	Date
Steve Sistare	a3eae205c6	migration: cpr-exec mode Add the cpr-exec migration mode. Usage: qemu-system-$arch -machine aux-ram-share=on ... migrate_set_parameter mode cpr-exec migrate_set_parameter cpr-exec-command \ <arg1> <arg2> ... -incoming <uri-1> \ migrate -d <uri-1> The migrate command stops the VM, saves state to uri-1, directly exec's a new version of QEMU on the same host, replacing the original process while retaining its PID, and loads state from uri-1. Guest RAM is preserved in place, albeit with new virtual addresses. The new QEMU process is started by exec'ing the command specified by the @cpr-exec-command parameter. The first word of the command is the binary, and the remaining words are its arguments. The command may be a direct invocation of new QEMU, or may be a non-QEMU command that exec's the new QEMU binary. This mode creates a second migration channel that is not visible to the user. At the start of migration, old QEMU saves CPR state to the second channel, and at the end of migration, it tells the main loop to call cpr_exec. New QEMU loads CPR state early, before objects are created. Because old QEMU terminates when new QEMU starts, one cannot stream data between the two, so uri-1 must be a type, such as a file, that accepts all data before old QEMU exits. Otherwise, old QEMU may quietly block writing to the channel. Memory-backend objects must have the share=on attribute, but memory-backend-epc is not supported. The VM must be started with the '-machine aux-ram-share=on' option, which allows anonymous memory to be transferred in place to the new process. The memfds are kept open across exec by clearing the close-on-exec flag, their values are saved in CPR state, and they are mmap'd in new QEMU. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Acked-by: Markus Armbruster <armbru@redhat.com> Link: https://lore.kernel.org/r/1759332851-370353-7-git-send-email-steven.sistare@oracle.com Signed-off-by: Peter Xu <peterx@redhat.com>	11 months ago
Steve Sistare	efc6587313	migration: cpr-exec save and load To preserve CPR state across exec, create a QEMUFile based on a memfd, and keep the memfd open across exec. Save the value of the memfd in an environment variable so post-exec QEMU can find it. These new functions are called in a subsequent patch. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Link: https://lore.kernel.org/r/1759332851-370353-6-git-send-email-steven.sistare@oracle.com [peterx: fix build for Windows] Signed-off-by: Peter Xu <peterx@redhat.com>	11 months ago
Steve Sistare	a9f9eee58b	migration: add cpr_walk_fd Add a helper to walk all CPR fd's and run a callback for each. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Peter Xu <peterx@redhat.com> Link: https://lore.kernel.org/r/1759332851-370353-3-git-send-email-steven.sistare@oracle.com Signed-off-by: Peter Xu <peterx@redhat.com>	11 months ago
Steve Sistare	a6f2f9c42f	migration: vfio cpr state hook Define a list of vfio devices in CPR state, in a subsection so that older QEMU can be live updated to this version. However, new QEMU will not be live updateable to old QEMU. This is acceptable because CPR is not yet commonly used, and updates to older versions are unusual. The contents of each device object will be defined by the vfio subsystem in a subsequent patch. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com> Link: https://lore.kernel.org/qemu-devel/1751493538-202042-14-git-send-email-steven.sistare@oracle.com Signed-off-by: Cédric Le Goater <clg@redhat.com>	1 year ago
Steve Sistare	ccfc6715cf	migration: cpr_get_fd_param helper Add the helper function cpr_get_fd_param, to use when preserving a file descriptor that is opened externally and passed to QEMU. cpr_get_fd_param returns a descriptor number either from a QEMU command-line parameter, from a getfd command, or from CPR state. When a descriptor is passed to new QEMU via SCM_RIGHTS, its number changes. Hence, during CPR, the command-line parameter is ignored in new QEMU, and over-ridden by the value found in CPR state. Similarly, if the descriptor was originally specified by a getfd command in old QEMU, the fd number is not known outside of QEMU, and it changes when sent to new QEMU via SCM_RIGHTS. Hence the user cannot send getfd to new QEMU, but when the user sends a hotplug command that references the fd, cpr_get_fd_param finds its value in CPR state. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Fabiano Rosas <farosas@suse.de> Link: https://lore.kernel.org/qemu-devel/1751493538-202042-5-git-send-email-steven.sistare@oracle.com Signed-off-by: Cédric Le Goater <clg@redhat.com>	1 year ago
Steve Sistare	f95fd60ac1	migration: cpr helpers Add the cpr_incoming_needed, cpr_open_fd, and cpr_resave_fd helpers, for use when adding cpr support for vfio and iommufd. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Cédric Le Goater <clg@redhat.com> Link: https://lore.kernel.org/qemu-devel/1749569991-25171-2-git-send-email-steven.sistare@oracle.com Signed-off-by: Cédric Le Goater <clg@redhat.com>	1 year ago
Steve Sistare	1632a2017f	migration: cpr_is_incoming Define the cpr_is_incoming helper, to be used in several cpr fix patches. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Fabiano Rosas <farosas@suse.de> Message-ID: <1741380954-341079-2-git-send-email-steven.sistare@oracle.com> Signed-off-by: Fabiano Rosas <farosas@suse.de>	1 year ago
Steve Sistare	624e6e654e	migration: cpr-transfer mode Add the cpr-transfer migration mode, which allows the user to transfer a guest to a new QEMU instance on the same host with minimal guest pause time, by preserving guest RAM in place, albeit with new virtual addresses in new QEMU, and by preserving device file descriptors. Pages that were locked in memory for DMA in old QEMU remain locked in new QEMU, because the descriptor of the device that locked them remains open. cpr-transfer preserves memory and devices descriptors by sending them to new QEMU over a unix domain socket using SCM_RIGHTS. Such CPR state cannot be sent over the normal migration channel, because devices and backends are created prior to reading the channel, so this mode sends CPR state over a second "cpr" migration channel. New QEMU reads the cpr channel prior to creating devices or backends. The user specifies the cpr channel in the channel arguments on the outgoing side, and in a second -incoming command-line parameter on the incoming side. The user must start old QEMU with the the '-machine aux-ram-share=on' option, which allows anonymous memory to be transferred in place to the new process by transferring a memory descriptor for each ram block. Memory-backend objects must have the share=on attribute, but memory-backend-epc is not supported. The user starts new QEMU on the same host as old QEMU, with command-line arguments to create the same machine, plus the -incoming option for the main migration channel, like normal live migration. In addition, the user adds a second -incoming option with channel type "cpr". This CPR channel must support file descriptor transfer with SCM_RIGHTS, i.e. it must be a UNIX domain socket. To initiate CPR, the user issues a migrate command to old QEMU, adding a second migration channel of type "cpr" in the channels argument. Old QEMU stops the VM, saves state to the migration channels, and enters the postmigrate state. New QEMU mmap's memory descriptors, and execution resumes. The implementation splits qmp_migrate into start and finish functions. Start sends CPR state to new QEMU, which responds by closing the CPR channel. Old QEMU detects the HUP then calls finish, which connects the main migration channel. In summary, the usage is: qemu-system-$arch -machine aux-ram-share=on ... start new QEMU with "-incoming <main-uri> -incoming <cpr-channel>" Issue commands to old QEMU: migrate_set_parameter mode cpr-transfer {"execute": "migrate", ... {"channel-type": "main"...}, {"channel-type": "cpr"...} ... } Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Peter Xu <peterx@redhat.com> Acked-by: Markus Armbruster <armbru@redhat.com> Link: https://lore.kernel.org/r/1736967650-129648-17-git-send-email-steven.sistare@oracle.com Signed-off-by: Fabiano Rosas <farosas@suse.de>	2 years ago
Steve Sistare	b3698869f4	migration: cpr-transfer save and load Add functions to create a QEMUFile based on a unix URI, for saving or loading, for use by cpr-transfer mode to preserve CPR state. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Peter Xu <peterx@redhat.com> Link: https://lore.kernel.org/r/1736967650-129648-16-git-send-email-steven.sistare@oracle.com Signed-off-by: Fabiano Rosas <farosas@suse.de>	2 years ago
Steve Sistare	e7d79011a4	migration: cpr-state CPR must save state that is needed after QEMU is restarted, when devices are realized. Thus the extra state cannot be saved in the migration channel, as objects must already exist before that channel can be loaded. Instead, define auxilliary state structures and vmstate descriptions, not associated with any registered object, and serialize the aux state to a cpr-specific channel in cpr_state_save. Deserialize in cpr_state_load after QEMU restarts, before devices are realized. Provide accessors for clients to register file descriptors for saving. The mechanism for passing the fd's to the new process will be specific to each migration mode, and added in subsequent patches. Signed-off-by: Steve Sistare <steven.sistare@oracle.com> Reviewed-by: Fabiano Rosas <farosas@suse.de> Reviewed-by: Peter Xu <peterx@redhat.com> Link: https://lore.kernel.org/r/1736967650-129648-8-git-send-email-steven.sistare@oracle.com Signed-off-by: Fabiano Rosas <farosas@suse.de>	2 years ago