/* SPDX-License-Identifier: BSD-3-Clause */
/*
* Copyright (C) 2019 - 2023 Intel Corporation
*/
#ifndef _UAPI_LINUX_UM_TIMETRAVEL_H
#define _UAPI_LINUX_UM_TIMETRAVEL_H
#include <linux/types.h>
/**
* struct um_timetravel_msg - UM time travel message
*
* This is the basic message type, going in both directions.
*
* This is the message passed between the host (user-mode Linux instance)
* and the calendar (the application on the other side of the socket) in
* order to implement common scheduling.
*
* Whenever UML has an event it will request runtime for it from the
* calendar, and then wait for its turn until it can run, etc. Note
* that it will only ever request the single next runtime, i.e. multiple
* REQUEST messages override each other.
*/
struct um_timetravel_msg {
/**
* @op: operation value from &enum um_timetravel_ops
*/
__u32 op;
/**
* @seq: sequence number for the message - shall be reflected in
* the ACK response, and should be checked while processing
* the response to see if it matches
*/
__u32 seq;
/**
* @time: time in nanoseconds
*/
__u64 time;
};
/* max number of file descriptors that can be sent/received in a message */
#define UM_TIMETRAVEL_MAX_FDS 2
/**
* enum um_timetravel_shared_mem_fds - fds sent in ACK message for START message
*/
enum um_timetravel_shared_mem_fds {
/**
* @UM_TIMETRAVEL_SHARED_MEMFD: Index of the shared memory file
* descriptor in the control message
*/
UM_TIMETRAVEL_SHARED_MEMFD,
/**
* @UM_TIMETRAVEL_SHARED_LOGFD: Index of the logging file descriptor
* in the control message
*/
UM_TIMETRAVEL_SHARED_LOGFD,
UM_TIMETRAVEL_SHARED_MAX_FDS,
};
/**
* enum um_timetravel_start_ack - ack-time mask for start message
*/
enum um_timetravel_start_ack {
/**
* @UM_TIMETRAVEL_START_ACK_ID: client ID that controller allocated.
*/
UM_TIMETRAVEL_START_ACK_ID = 0xffff,
};
/**
* enum um_timetravel_ops - Operation codes
*/
enum um_timetravel_ops {
/**
* @UM_TIMETRAVEL_ACK: response (ACK) to any previous message,
* this usually doesn't carry any data in the 'time' field
* unless otherwise specified below, note: while using shared
* memory no ACK for WAIT and RUN messages, for more info see
* &struct um_timetravel_schedshm.
*/
UM_TIMETRAVEL_ACK = 0,
/**
* @UM_TIMETRAVEL_START: initialize the connection, the time
* field contains an (arbitrary) ID to possibly be able
* to distinguish the connections.
*/
UM_TIMETRAVEL_START = 1,
/**
* @UM_TIMETRAVEL_REQUEST: request to run at the given time
* (host -> calendar)
*/
UM_TIMETRAVEL_REQUEST = 2,
/**
* @UM_TIMETRAVEL_WAIT: Indicate waiting for the previously requested
* runtime, new requests may be made while waiting (e.g. due to
* interrupts); the time field is ignored. The calendar must process
* this message and later send a %UM_TIMETRAVEL_RUN message when
* the host can run again.
* (host -> calendar)
*/
UM_TIMETRAVEL_WAIT = 3,
/**
* @UM_TIMETRAVEL_GET: return the current time from the calendar in the
* ACK message, the time in the request message is ignored
* (host -> calendar)
*/
UM_TIMETRAVEL_GET = 4,
/**
* @UM_TIMETRAVEL_UPDATE: time update to the calendar, must be sent e.g.
* before kicking an interrupt to another calendar
* (host -> calendar)
*/
UM_TIMETRAVEL_UPDATE = 5,
/**
* @UM_TIMETRAVEL_RUN: run time request granted, current time is in
* the time field
* (calendar -> host)
*/
UM_TIMETRAVEL_RUN = 6,
/**
* @UM_TIMETRAVEL_FREE_UNTIL: Enable free-running until the given time,
* this is a message from the calendar telling the host that it can
* freely do its own scheduling for anything before the indicated
* time.
* Note that if a calendar sends this message once, the host may
* assume that it will also do so in the future, if it implements
* wraparound semantics for the time field.
* (calendar -> host)
*/
UM_TIMETRAVEL_FREE_UNTIL = 7,
/**
* @UM_TIMETRAVEL_GET_TOD: Return time of day, typically used once at
* boot by the virtual machines to get a synchronized time from
* the simulation.
*/
UM_TIMETRAVEL_GET_TOD = 8,
/**
* @UM_TIMETRAVEL_BROADCAST: Send/Receive a broadcast message.
* This message can be used to sync all components in the system
* with a single message, if the calender gets the message, the
* calender broadcast the message to all components, and if a
* component receives it it should act based on it e.g print a
* message to it's log system.
* (calendar <-> host)
*/
UM_TIMETRAVEL_BROADCAST = 9,
};
/* version of struct um_timetravel_schedshm */
#define UM_TIMETRAVEL_SCHEDSHM_VERSION 2
/**
* enum um_timetravel_schedshm_cap - time travel capabilities of every client
*
* These flags must be set immediately after processing the ACK to
* the START message, before sending any message to the controller.
*/
enum um_timetravel_schedshm_cap {
/**
* @UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE: client can read current time
* update internal time request to shared memory and read
* free until and send no Ack on RUN and doesn't expect ACK on
* WAIT.
*/
UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE = 0x1,
};
/**
* enum um_timetravel_schedshm_flags - time travel flags of every client
*/
enum um_timetravel_schedshm_flags {
/**
* @UM_TIMETRAVEL_SCHEDSHM_FLAGS_REQ_RUN: client has a request to run.
* It's set by client when it has a request to run, if (and only
* if) the @running_id points to a client that is able to use
* shared memory, i.e. has %UM_TIMETRAVEL_SCHEDSHM_CAP_TIME_SHARE
* (this includes the client itself). Otherwise, a message must
* be used.
*/
UM_TIMETRAVEL_SCHEDSHM_FLAGS_REQ_RUN = 0x1,
};
/**
* DOC: Time travel shared memory overview
*
* The main purpose of the shared memory is to avoid all time travel message
* that don't need any action, for example current time can be held in shared
* memory without the need of any client to send a message UM_TIMETRAVEL_GET
* in order to know what's the time.
*
* Since this is shared memory with all clients and controller and controller
* creates the shared memory space, all time values are absolute to controller
* time. So first time client connects to shared memory mode it should take the
* current_time value in shared memory and keep it internally as a diff to
* shared memory times, and once shared memory is initialized, any interaction
* with the controller must happen in the controller time domain, including any
* messages (for clients that are not using shared memory, the controller will
* handle an offset and make the clients think they start at time zero.)
*
* Along with the shared memory file descriptor is sent to the client a logging
* file descriptor, to have all logs related to shared memory,
* logged into one place. note: to have all logs synced into log file at write,
* file should be flushed (fflush) after writing to it.
*
* To avoid memory corruption, we define below for each field who can write to
* it at what time, defined in the structure fields.
*
* To avoid having to pack this struct, all fields in it must be naturally aligned
* (i.e. aligned to their size).
*/
/**
* union um_timetravel_schedshm_client - UM time travel client struct
*
* Every entity using the shared memory including the controller has a place in
* the um_timetravel_schedshm clients array, that holds info related to the client
* using the shared memory, and can be set only by the client after it gets the
* fd memory.
*
* @capa: bit fields with client capabilities see
* &enum um_timetravel_schedshm_cap, set by client once after getting the
* shared memory file descriptor.
* @flags: bit fields for flags see &enum um_timetravel_schedshm_flags for doc.
* @req_time: request time to run, set by client on every request it needs.
* @name: unique id sent to the controller by client with START message.
*/
union um_timetravel_schedshm_client {
struct {
__u32 capa;
__u32 flags;
__u64 req_time;
__u64 name;
};
char reserve[128]; /* reserved for future usage */
};
/**
* struct um_timetravel_schedshm - UM time travel shared memory struct
*
* @hdr: header fields:
* @version: Current version struct UM_TIMETRAVEL_SCHEDSHM_VERSION,
* set by controller once at init, clients must check this after mapping
* and work without shared memory if they cannot handle the indicated
* version.
* @len: Length of all the memory including header (@hdr), clients should once
* per connection first mmap the header and take the length (@len) to remap the entire size.
* This is done in order to support dynamic struct size letting number of
* clients be dynamic based on controller support.
* @free_until: Stores the next request to run by any client, in order for the
* current client to know how long it can still run. A client needs to (at
* least) reload this value immediately after communicating with any other
* client, since the controller will update this field when a new request
* is made by any client. Clients also must update this value when they
* insert/update an own request into the shared memory while not running
* themselves, and the new request is before than the current value.
* current_time: Current time, can only be set by the client in running state
* (indicated by @running_id), though that client may only run until @free_until,
* so it must remain smaller than @free_until.
* @running_id: The current client in state running, set before a client is
* notified that it's now running.
* @max_clients: size of @clients array, set once at init by the controller.
* @clients: clients array see &union um_timetravel_schedshm_client for doc,
* set only by client.
*/
struct um_timetravel_schedshm {
union {
struct {
__u32 version;
__u32 len;
__u64 free_until;
__u64 current_time;
__u16 running_id;
__u16 max_clients;
};
char hdr[4096]; /* align to 4K page size */
};
union um_timetravel_schedshm_client clients[];
};
#endif /* _UAPI_LINUX_UM_TIMETRAVEL_H */
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