On Mon, Feb 27, 2023 at 10:53:45AM -0500, Stefan Hajnoczi wrote:
> On Fri, Feb 24, 2023 at 03:37:51PM +0100, David Heidelberg wrote:
> > From: Stefan Hajnoczi
> >
> > Make it possible to boot directly from a virtiofs file system with tag
> > 'myfs' using the following kernel parameters:
> >
> > rootfstype=virtiofs root=myfs rw
> >
> > Booting directly from virtiofs makes it possible to use a directory on
> > the host as the root file system. This is convenient for testing and
> > situations where manipulating disk image files is cumbersome.
> >
> > Reviewed-by: Helen Koike
> > Signed-off-by: Stefan Hajnoczi
> > Signed-off-by: David Heidelberg
> > ---
> > v2: added Reviewed-by and CCed everyone interested.
> >
> > We have used this option in Mesa3D CI for testing crosvm for
> > more than one years and it's proven to work reliably.
> >
> > We are working on effort to removing custom patches to be able to do
> > automated apply and test of patches from any tree.
> >
> >
> > https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/.gitlab-ci/crosvm-runner.sh#L85
> > init/do_mounts.c | 10 ++
> > 1 file changed, 10 insertions(+)
>
> Vivek, do you remember where we ended up with boot from virtiofs? I
> thought a different solution was merged some time ago.
We merged a patch from Christoph Hellwig to support this.
commit f9259be6a9e7c22d92e5a5000913147ae17e8321
Author: Christoph Hellwig
Date: Wed Jul 14 16:23:20 2021 -0400
init: allow mounting arbitrary non-blockdevice filesystems as root
Now one should be able to mount virtiofs using following syntax.
"root=myfs rootfstype=virtiofs rw"
IIUC, this patch should not be required anymore.
Thanks
Vivek
>
> There is documentation from the virtiofs community here:
> https://virtio-fs.gitlab.io/howto-boot.html
>
> Stefan
>
> >
> > diff --git a/init/do_mounts.c b/init/do_mounts.c
> > index 811e94daf0a8..11c11abe23d7 100644
> > --- a/init/do_mounts.c
> > +++ b/init/do_mounts.c
> > @@ -578,6 +578,16 @@ void __init mount_root(void)
> > printk(KERN_ERR "VFS: Unable to mount root fs via
> > SMB.\n");
> > return;
> > }
> > +#endif
> > +#ifdef CONFIG_VIRTIO_FS
> > + if (root_fs_names && !strcmp(root_fs_names, "virtiofs")) {
> > + if (!do_mount_root(root_device_name, "virtiofs",
> > + root_mountflags, root_mount_data))
> > + return;
> > +
> > + panic("VFS: Unable to mount root fs \"%s\" from virtiofs",
> > + root_device_name);
> > + }
> > #endif
> > if (ROOT_DEV == 0 && root_device_name && root_fs_names) {
> > if (mount_nodev_root() == 0)
> > --
> > 2.39.1
> >
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