From: "Alex Bennée" <alex.bennee@linaro.org>
To: QEMU Developers <qemu-devel@nongnu.org>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
virtio-fs@redhat.com, Erik Schilling <erik.schilling@linaro.org>
Subject: [Virtio-fs] Status of DAX for virtio-fs/virtiofsd?
Date: Wed, 17 May 2023 16:23:46 +0100 [thread overview]
Message-ID: <87v8grlzu9.fsf@linaro.org> (raw)
Hi,
I remember from the dim and distant past (probably a KVM Forum) that one
of the touted features of virtio-fs was the ability to get memory
efficiency savings by having a direct memory mapping the host pages into
the guest address space.
AFAICT the kernel side was merged a while ago, see 22f3787 (virtiofs:
set up virtio_fs dax_device) and related. However when investigating
what would be needed to support this for Xen guests using virtio-fs we
were confused as to what else was needed.
There were some patches for the old C daemon:
Subject: [PATCH v3 00/26] virtiofs dax patches
Date: Wed, 28 Apr 2021 12:00:34 +0100 [thread overview]
Message-ID: <20210428110100.27757-1-dgilbert@redhat.com>
although they look like they were never merged and the C version of
virtiofsd has since been dropped from tools.
Looking at the supporting rust code (vhost_user/message.rs) there are a
number of additional messages:
/// Virtio-fs draft: map file content into the window.
FS_MAP = 6,
/// Virtio-fs draft: unmap file content from the window.
FS_UNMAP = 7,
/// Virtio-fs draft: sync file content.
FS_SYNC = 8,
/// Virtio-fs draft: perform a read/write from an fd directly to GPA.
FS_IO = 9,
/// Upper bound of valid commands.
MAX_CMD = 10,
that don't appear in the current canonical vhost-user reference in the
QEMU repository and the QEMU code certainly doesn't have implementations
for any of them. So I have some questions:
* What VMM/daemon combinations has DAX been tested on?
* Isn't it time the vhost-user spec is updated?
* Is anyone picking up Dave's patches for the QEMU side of support?
Thanks,
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
next reply other threads:[~2023-05-17 15:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 15:23 Alex Bennée [this message]
2023-05-17 16:26 ` [Virtio-fs] Status of DAX for virtio-fs/virtiofsd? Stefan Hajnoczi
2023-05-18 19:45 ` Vivek Goyal
2023-05-22 12:54 ` Alex Bennée
2023-09-06 13:07 ` Hao Xu
2023-09-06 13:57 ` Stefan Hajnoczi
2023-09-07 4:19 ` Hao Xu
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=87v8grlzu9.fsf@linaro.org \
--to=alex.bennee@linaro.org \
--cc=erik.schilling@linaro.org \
--cc=qemu-devel@nongnu.org \
--cc=stefanha@redhat.com \
--cc=virtio-fs@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 read-only IMAP folder(s) and NNTP newsgroup(s).