From: Wei Liu <wei.liu2@citrix.com>
To: Anthony PERARD <anthony.perard@citrix.com>
Cc: xen-devel@lists.xenproject.org, Wei Liu <wei.liu2@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>
Subject: Re: [RFC v2 6/9] libxl: Have QEMU save its state to a file descriptor
Date: Tue, 24 Apr 2018 10:37:46 +0100 [thread overview]
Message-ID: <20180424093746.5e4mj6fm4kxmlhfs@citrix.com> (raw)
In-Reply-To: <20180423154528.GE1980@perard>
On Mon, Apr 23, 2018 at 04:45:28PM +0100, Anthony PERARD wrote:
> On Mon, Apr 23, 2018 at 10:20:42AM +0100, Wei Liu wrote:
> > On Mon, Apr 16, 2018 at 06:32:24PM +0100, Anthony PERARD wrote:
> > > In case QEMU have restricted access to the system, open the file for it,
> > > and QEMU will save its state to this file descritor.
> > >
> > > Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> >
> > I think this is going to break FreeBSD?
>
> If the previous patch works on FreeBSD (Learned to send FD through QMP
> to QEMU), this patch shouldn't break anything. Looking at how
> libxl__sendmsg_fds() is implemented, and how the receive side is
> implemented in QEMU, there doesn't seems to be any difference on
> FreeBSD, so I guess it's going to work fine.
>
> > And what is /dev/fdset exactly? I don't seem to have it on my Debian
> > workstation (with Linux 4.15). So this change can potentially be broken
> > on Linux as well?
>
> /dev/fdset is a QEMU internal API. You can add a file descriptor to a
> fd-set via QMP or via the command line. And later, you can give a path
> to something in QEMU (maybe a block driver) which refer to a fd-set
> created earlier. The path would be "/dev/fdset/$fdset_number". There can
> be several fd in a fd-set, qemu will just look for the first one which
> have the right permission, like read or write permission.
Oh, I was thinking /dev/fdset was some sort of Linux specific thing. It
is interesting that QEMU actually creates /dev/fdset. That means it
should work fine (at least in theory) for both FreeBSD and Linux.
Wei.
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next prev parent reply other threads:[~2018-04-24 9:37 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-16 17:32 [RFC v2 0/9] libxl: Enable save/restore/migration of a restricted QEMU Anthony PERARD
2018-04-16 17:32 ` [RFC v2 1/9] libxl_event: Fix DEBUG prints Anthony PERARD
2018-04-19 8:17 ` Wei Liu
2018-04-19 11:01 ` Anthony PERARD
2018-04-16 17:32 ` [RFC v2 2/9] libxl_qmp: Documentation of the logic of the QMP client Anthony PERARD
2018-04-19 8:19 ` Wei Liu
2018-04-16 17:32 ` [RFC v2 3/9] libxl_qmp: Fix use of DEBUG_RECEIVED Anthony PERARD
2018-04-19 8:22 ` Wei Liu
2018-04-16 17:32 ` [RFC v2 4/9] libxl_qmp: Move the buffer realloc to the same scope level as read Anthony PERARD
2018-04-23 9:03 ` Wei Liu
2018-04-23 14:50 ` Anthony PERARD
2018-04-23 15:01 ` Wei Liu
2018-04-16 17:32 ` [RFC v2 5/9] libxl: Learned to send FD through QMP to QEMU Anthony PERARD
2018-04-23 9:04 ` Wei Liu
2018-04-16 17:32 ` [RFC v2 6/9] libxl: Have QEMU save its state to a file descriptor Anthony PERARD
2018-04-23 9:20 ` Wei Liu
2018-04-23 15:45 ` Anthony PERARD
2018-04-24 9:37 ` Wei Liu [this message]
2018-04-24 9:46 ` Wei Liu
2018-04-16 17:32 ` [RFC v2 7/9] libxl_qmp: Implement query-status command Anthony PERARD
2018-04-23 9:24 ` Wei Liu
2018-04-16 17:32 ` [RFC v2 8/9] HACK libxl_exec: Check QEMU status via QMP instead of xenstore Anthony PERARD
2018-04-16 18:09 ` Anthony PERARD
2018-04-17 9:18 ` Anthony PERARD
2018-04-20 18:37 ` Ian Jackson
2018-04-23 16:54 ` Anthony PERARD
2018-04-23 16:56 ` Ian Jackson
2018-04-16 17:32 ` [RFC v2 9/9] libxl_qmp: Add a warning to not trust QEMU Anthony PERARD
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