On Fri, Feb 14, 2025 at 06:13:44AM -0800, Steve Sistare wrote:
> Add cpr_needed_for_reuse, cpr_resave_fd helpers, cpr_is_incoming, and
> cpr_open_fd, for use when adding cpr support for vfio and iommufd.
>
> Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
> ---
> include/migration/cpr.h | 6 ++++++
> migration/cpr.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 50 insertions(+)
>
> diff --git a/include/migration/cpr.h b/include/migration/cpr.h
> index 3a6deb7..6ad04d4 100644
> --- a/include/migration/cpr.h
> +++ b/include/migration/cpr.h
> @@ -18,15 +18,21 @@
> void cpr_save_fd(const char *name, int id, int fd);
> void cpr_delete_fd(const char *name, int id);
> int cpr_find_fd(const char *name, int id);
> +void cpr_resave_fd(const char *name, int id, int fd);
> +int cpr_open_fd(const char *path, int flags, const char *name, int id,
> + bool *reused, Error **errp);
>
> MigMode cpr_get_incoming_mode(void);
> void cpr_set_incoming_mode(MigMode mode);
> +bool cpr_is_incoming(void);
>
> int cpr_state_save(MigrationChannel *channel, Error **errp);
> int cpr_state_load(MigrationChannel *channel, Error **errp);
> void cpr_state_close(void);
> struct QIOChannel *cpr_state_ioc(void);
>
> +bool cpr_needed_for_reuse(void *opaque);
> +
> QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp);
> QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp);
>
> diff --git a/migration/cpr.c b/migration/cpr.c
> index 584b0b9..12c489b 100644
> --- a/migration/cpr.c
> +++ b/migration/cpr.c
> @@ -95,6 +95,39 @@ int cpr_find_fd(const char *name, int id)
> trace_cpr_find_fd(name, id, fd);
> return fd;
> }
> +
> +void cpr_resave_fd(const char *name, int id, int fd)
> +{
> + CprFd *elem = find_fd(&cpr_state.fds, name, id);
> + int old_fd = elem ? elem->fd : -1;
> +
> + if (old_fd < 0) {
> + cpr_save_fd(name, id, fd);
> + } else if (old_fd != fd) {
> + error_setg(&error_fatal,
> + "internal error: cpr fd '%s' id %d value %d "
> + "already saved with a different value %d",
> + name, id, fd, old_fd);
How bad it is to trigger this?
I wonder if cpr_save_fd() should have checked this already on duplicated
entries; it looks risky there too if this happens to existing cpr_save_fd()
callers.
> + }
> +}
> +
> +int cpr_open_fd(const char *path, int flags, const char *name, int id,
> + bool *reused, Error **errp)
> +{
> + int fd = cpr_find_fd(name, id);
> +
> + if (reused) {
> + *reused = (fd >= 0);
> + }
> + if (fd < 0) {
> + fd = qemu_open(path, flags, errp);
> + if (fd >= 0) {
> + cpr_save_fd(name, id, fd);
> + }
> + }
> + return fd;
> +}
> +
> /*************************************************************************/
> #define CPR_STATE "CprState"
>
> @@ -128,6 +161,11 @@ void cpr_set_incoming_mode(MigMode mode)
> incoming_mode = mode;
> }
>
> +bool cpr_is_incoming(void)
> +{
> + return incoming_mode != MIG_MODE_NONE;
> +}
Maybe it'll be helpful to document either this function or incoming_mode;
it's probably not yet obvious to most readers incoming_mode is only set to
!NONE during a small window when VM loads.
> +
> int cpr_state_save(MigrationChannel *channel, Error **errp)
> {
> int ret;
> @@ -222,3 +260,9 @@ void cpr_state_close(void)
> cpr_state_file = NULL;
> }
> }
> +
> +bool cpr_needed_for_reuse(void *opaque)
> +{
> + MigMode mode = migrate_mode();
Nit: can drop the var.
> + return mode == MIG_MODE_CPR_TRANSFER;
> +}
> --
> 1.8.3.1
>
--
Peter Xu
