From: Wei Liu <wei.liu2@citrix.com>
To: Anthony PERARD <anthony.perard@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
Ian Jackson <Ian.Jackson@eu.citrix.com>,
Jan Beulich <JBeulich@suse.com>
Subject: Re: [PATCH 3/3] libxl: update vcpus bitmap in retrieved guest config
Date: Tue, 7 Jun 2016 17:03:07 +0100 [thread overview]
Message-ID: <20160607160307.GN25922@citrix.com> (raw)
In-Reply-To: <20160607144529.GL1184@perard.uk.xensource.com>
On Tue, Jun 07, 2016 at 03:45:29PM +0100, Anthony PERARD wrote:
> On Tue, Jun 07, 2016 at 12:24:02PM +0100, Wei Liu wrote:
> > ... because the available vcpu bitmap can change during domain life time
> > due to cpu hotplug and unplug.
> >
> > For QEMU upstream, we interrogate QEMU for the number of vcpus. For
> > others, we look directly into xenstore for information.
> >
> > Reported-by: Jan Beulich <jbeulich@suse.com>
> > Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> > ---
> > tools/libxl/libxl.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 91 insertions(+)
> >
> > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> > index 006b83f..4f8b663 100644
> > --- a/tools/libxl/libxl.c
> > +++ b/tools/libxl/libxl.c
> > @@ -7222,6 +7222,57 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, libxl_mac *src)
> > (*dst)[i] = (*src)[i];
> > }
> >
> > +static int libxl__update_avail_vcpus_qmp(libxl__gc *gc, uint32_t domid,
> > + unsigned int max_vcpus,
> > + libxl_bitmap *map)
> > +{
> > + unsigned int count, i;
> > + int rc;
> > +
> > + /* For QEMU upstream we always need to return the number
> > + * of cpus present to QEMU whether they are online or not;
> > + * otherwise QEMU won't accept the saved state.
> > + */
> > + rc = libxl__qmp_query_cpus(gc, domid, &count);
> > + if (rc) {
> > + LOG(ERROR, "fail to get number of cpus for domain %d", domid);
> > + goto out;
> > + }
> > +
> > + for (i = 0; i < count; i++)
> > + libxl_bitmap_set(map, i);
>
> What if I have cpu 1, 7 and 42 online, but all the other offline?
>
I have more or less the same question when I wrote this patch. At that
time I thought the avail_vcpus was only used for generating -smp option
to QEMU.
In your example, you will have -smp 3,maxvcpus=$Y. I think the migration
should still succeed. Furthermore, the cpu-add operation doesn't care,
so it probably won't have visible effect.
I agree it would be good to set the exact bits though -- if you can tell
me which field to test.
-> { "execute": "query-cpus" }
<- {
"return":[
{
"CPU":0,
"current":true,
"halted":false,
"qom_path":"/machine/unattached/device[0]",
"arch":"x86",
"pc":3227107138,
"thread_id":3134
},
{
"CPU":1,
"current":false,
"halted":true,
"qom_path":"/machine/unattached/device[2]",
"arch":"x86",
"pc":7108165,
"thread_id":3135
}
]
}
EQMP
Wei.
> --
> Anthony PERARD
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next prev parent reply other threads:[~2016-06-07 16:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-07 11:23 [PATCH 0/3] libxl: update available vcpus map in retrieve configuration function Wei Liu
2016-06-07 11:24 ` [PATCH 1/3] libxl: introduce libxl__json_array_count Wei Liu
2016-06-07 11:24 ` [PATCH 2/3] libxl: introduce libxl__qmp_query_cpus Wei Liu
2016-06-07 11:24 ` [PATCH 3/3] libxl: update vcpus bitmap in retrieved guest config Wei Liu
2016-06-07 14:45 ` Anthony PERARD
2016-06-07 16:03 ` Wei Liu [this message]
2016-06-07 16:22 ` Dario Faggioli
2016-06-07 16:46 ` Wei Liu
2016-06-07 17:05 ` Dario Faggioli
2016-06-07 16:36 ` Anthony PERARD
2016-06-07 16:39 ` Wei Liu
2016-06-14 16:31 ` Ian Jackson
2016-06-14 16:39 ` Wei Liu
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