From: Peter Xu <peterx@redhat.com>
To: Avihai Horon <avihaih@nvidia.com>
Cc: qemu-devel@nongnu.org,
"Alex Williamson" <alex.williamson@redhat.com>,
"Cédric Le Goater" <clg@redhat.com>,
"Juan Quintela" <quintela@redhat.com>,
"Leonardo Bras" <leobras@redhat.com>,
"Yanghang Liu" <yanghliu@redhat.com>
Subject: Re: [PATCH v2 5/5] vfio/migration: Block VFIO migration with background snapshot
Date: Fri, 1 Sep 2023 11:51:22 -0400 [thread overview]
Message-ID: <ZPIIeqj8VMyDz7iY@x1n> (raw)
In-Reply-To: <20230831125702.11263-6-avihaih@nvidia.com>
On Thu, Aug 31, 2023 at 03:57:02PM +0300, Avihai Horon wrote:
> Background snapshot allows creating a snapshot of the VM while it's
> running and keeping it small by not including dirty RAM pages.
>
> The way it works is by first stopping the VM, saving the non-iterable
> devices' state and then starting the VM and saving the RAM while write
> protecting it with UFFD. The resulting snapshot represents the VM state
> at snapshot start.
>
> VFIO migration is not compatible with background snapshot.
> First of all, VFIO device state is not even saved in background snapshot
> because only non-iterable device state is saved. But even if it was
> saved, after starting the VM, a VFIO device could dirty pages without it
> being detected by UFFD write protection. This would corrupt the
> snapshot, as the RAM in it would not represent the RAM at snapshot
> start.
>
> To prevent this, block VFIO migration with background snapshot.
>
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
--
Peter Xu
prev parent reply other threads:[~2023-09-01 15:52 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-31 12:56 [PATCH v2 0/5] vfio/migration: Block VFIO migration with postcopy and background snapshot Avihai Horon
2023-08-31 12:56 ` [PATCH v2 1/5] migration: Add migration prefix to functions in target.c Avihai Horon
2023-08-31 12:56 ` [PATCH v2 2/5] vfio/migration: Fail adding device with enable-migration=on and existing blocker Avihai Horon
2023-08-31 12:57 ` [PATCH v2 3/5] migration: Add .save_prepare() handler to struct SaveVMHandlers Avihai Horon
2023-09-01 15:49 ` Peter Xu
2023-09-05 16:13 ` Cédric Le Goater
2023-09-06 14:11 ` Avihai Horon
2023-09-06 14:21 ` Cédric Le Goater
2023-08-31 12:57 ` [PATCH v2 4/5] vfio/migration: Block VFIO migration with postcopy migration Avihai Horon
2023-09-01 10:14 ` YangHang Liu
2023-09-01 15:51 ` Peter Xu
2023-09-03 7:52 ` Avihai Horon
2023-08-31 12:57 ` [PATCH v2 5/5] vfio/migration: Block VFIO migration with background snapshot Avihai Horon
2023-09-01 15:51 ` Peter Xu [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ZPIIeqj8VMyDz7iY@x1n \
--to=peterx@redhat.com \
--cc=alex.williamson@redhat.com \
--cc=avihaih@nvidia.com \
--cc=clg@redhat.com \
--cc=leobras@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=quintela@redhat.com \
--cc=yanghliu@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).