* Use of migrate_add_blocker() in qxl.c
@ 2021-07-10 6:51 Markus Armbruster
0 siblings, 0 replies; only message in thread
From: Markus Armbruster @ 2021-07-10 6:51 UTC (permalink / raw)
To: Gerd Hoffmann; +Cc: qemu-devel
migrate_add_blocker() fails when running with --only-migratable, and
when migration is in progress.
qxl.c continues after migrate_add_blocker() fails:
{
/*
* Windows 8 drivers place qxl commands in the vram
* (instead of the ram) bar. We can't live migrate such a
* guest, so add a migration blocker in case we detect
* this, to avoid triggering the assert in pre_save().
*
* https://cgit.freedesktop.org/spice/win32/qxl-wddm-dod/commit/?id=f6e099db39e7d0787f294d5fd0dce328b5210faa
*/
void *msg = qxl_phys2virt(qxl, ext->cmd.data, ext->group_id);
if (msg != NULL && (
msg < (void *)qxl->vga.vram_ptr ||
msg > ((void *)qxl->vga.vram_ptr + qxl->vga.vram_size))) {
if (!qxl->migration_blocker) {
Error *local_err = NULL;
error_setg(&qxl->migration_blocker,
"qxl: guest bug: command not in ram bar");
migrate_add_blocker(qxl->migration_blocker, &local_err);
if (local_err) {
error_report_err(local_err);
}
}
}
}
Why is this safe? If the blocker is needed to prevent a crash, as the
comment says, then what prevents the crash when adding the blocker
fails?
Code goes back to
commit 86dbcdd9c7590d06db89ca256c5eaf0b4aba8858
Author: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon Apr 10 13:31:31 2017 +0200
qxl: add migration blocker to avoid pre-save assert
Cc: 1635339@bugs.launchpad.net
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20170410113131.2585-1-kraxel@redhat.com
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2021-07-10 6:52 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-10 6:51 Use of migrate_add_blocker() in qxl.c Markus Armbruster
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).