From: Fabiano Rosas <farosas@suse.de>
To: Peter Xu <peterx@redhat.com>, qemu-devel@nongnu.org
Cc: "Prasad Pandit" <ppandit@redhat.com>,
"Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
"Cédric Le Goater" <clg@redhat.com>,
"Alex Williamson" <alex.williamson@redhat.com>,
peterx@redhat.com, "Avihai Horon" <avihaih@nvidia.com>
Subject: Re: [PATCH v3 7/7] migration/multifd: Document the reason to sync for save_setup()
Date: Mon, 09 Dec 2024 17:56:12 -0300 [thread overview]
Message-ID: <87r06ga843.fsf@suse.de> (raw)
In-Reply-To: <20241206224755.1108686-8-peterx@redhat.com>
Peter Xu <peterx@redhat.com> writes:
> It's not straightforward to see why src QEMU needs to sync multifd during
> setup() phase. After all, there's no page queued at that point.
>
> For old QEMUs, there's a solid reason: EOS requires it to work. While it's
> clueless on the new QEMUs which do not take EOS message as sync requests.
>
> One will figure that out only when this is conditionally removed. In fact,
> the author did try it out. Logically we could still avoid doing this on
> new machine types, however that needs a separate compat field and that can
> be an overkill in some trivial overhead in setup() phase.
>
> Let's instead document it completely, to avoid someone else tries this
> again and do the debug one more time, or anyone confused on why this ever
> existed.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
next prev parent reply other threads:[~2024-12-09 20:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-06 22:47 [PATCH v3 0/7] migration/multifd: Some VFIO / postcopy preparations on flush Peter Xu
2024-12-06 22:47 ` [PATCH v3 1/7] migration/multifd: Further remove the SYNC on complete Peter Xu
2024-12-06 22:47 ` [PATCH v3 2/7] migration/multifd: Allow to sync with sender threads only Peter Xu
2024-12-09 20:52 ` Fabiano Rosas
2024-12-06 22:47 ` [PATCH v3 3/7] migration/ram: Move RAM_SAVE_FLAG* into ram.h Peter Xu
2024-12-06 22:47 ` [PATCH v3 4/7] migration/multifd: Unify RAM_SAVE_FLAG_MULTIFD_FLUSH messages Peter Xu
2024-12-06 22:47 ` [PATCH v3 5/7] migration/multifd: Remove sync processing on postcopy Peter Xu
2024-12-06 22:47 ` [PATCH v3 6/7] migration/multifd: Cleanup src flushes on condition check Peter Xu
2024-12-09 20:55 ` Fabiano Rosas
2024-12-06 22:47 ` [PATCH v3 7/7] migration/multifd: Document the reason to sync for save_setup() Peter Xu
2024-12-09 20:56 ` Fabiano Rosas [this message]
2024-12-17 15:26 ` [PATCH v3 0/7] migration/multifd: Some VFIO / postcopy preparations on flush Fabiano Rosas
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