From: Wei Liu <wei.liu2@citrix.com>
To: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Jan Beulich <JBeulich@suse.com>,
Anthony PERARD <anthony.perard@citrix.com>,
xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: "xl vcpu-set" not persistent across reboot?
Date: Tue, 14 Jun 2016 18:23:52 +0100 [thread overview]
Message-ID: <20160614172352.GU28116@citrix.com> (raw)
In-Reply-To: <20160614170301.GS28116@citrix.com>
On Tue, Jun 14, 2016 at 06:03:01PM +0100, Wei Liu wrote:
> On Tue, Jun 14, 2016 at 05:57:00PM +0100, Ian Jackson wrote:
> > Wei Liu writes ("Re: [Xen-devel] "xl vcpu-set" not persistent across reboot?"):
> > > What Andrew means is that QEMU shouldn't have kept the CPU state
> > > structures in the first place. My response explains why that is not
> > > possible from a QEMU upstream point of view.
> >
> > I don't think it addresses my point.
> >
> > > Hence the unfortunate fact is that we need to live with it for now. To
> > > start QEMU we need to create a bunch of dummy CPUs to keep QEMU happy.
> > > All those dummy states need to be kept.
> >
> > Why do we need one dummy state per actual vcpu rather than just one
> > dummy state no matter how many vcpus ?
> >
>
> We can't because ...
>
> > Or is qemu involved in hvm cpu hotplug ?
> >
>
> when doing hotplug, libxl uses QMP command to tell QEMU to create
> CPUs.
>
> Whether this can be changed I will let Anthony and Stefano to answer.
>
OK, a quick check shows that the current state of affairs does require
QEMU to get involved.
If we skip the QMP call, guest gets no new cpus -- CPU hotplug is
completely broken.
Wei.
---8<---
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 0e2c15a..1cd8e00 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -5756,6 +5756,8 @@ static int libxl__set_vcpuonline_qmp(libxl__gc
*gc, uint32_t domid,
int i, rc;
libxl_bitmap current_map, final_map;
+ return 0;
+
libxl_bitmap_init(¤t_map);
libxl_bitmap_init(&final_map);
> Wei.
>
> > Ian.
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next prev parent reply other threads:[~2016-06-14 17:24 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-03 8:29 "xl vcpu-set" not persistent across reboot? Jan Beulich
2016-06-03 13:41 ` Wei Liu
2016-06-03 14:42 ` Jan Beulich
2016-06-03 16:35 ` Wei Liu
2016-06-06 8:58 ` Jan Beulich
2016-06-06 17:18 ` Wei Liu
2016-06-06 17:20 ` Wei Liu
2016-06-06 17:34 ` Andrew Cooper
2016-06-07 8:30 ` Wei Liu
2016-06-14 16:34 ` Ian Jackson
2016-06-14 16:39 ` Wei Liu
2016-06-14 16:57 ` Ian Jackson
2016-06-14 16:59 ` Andrew Cooper
2016-06-14 17:06 ` Wei Liu
2016-06-14 17:03 ` Wei Liu
2016-06-14 17:23 ` Wei Liu [this message]
2016-06-14 17:35 ` Anthony PERARD
2016-06-07 6:38 ` Jan Beulich
2016-06-07 8:27 ` Wei Liu
2016-06-06 9:04 Jan Beulich
2016-06-06 13:07 ` Stefano Stabellini
2016-06-06 13:42 ` Wei Liu
2016-06-06 14:00 ` Stefano Stabellini
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