From: "Xia, Hongyan" <hongyxia@amazon.com>
To: "wl@xen.org" <wl@xen.org>,
"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"Grall, Julien" <jgrall@amazon.com>,
"jbeulich@suse.com" <jbeulich@suse.com>,
"roger.pau@citrix.com" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v2] x86/domain_page: implement pure per-vCPU mapping infrastructure
Date: Fri, 21 Feb 2020 14:40:14 +0000 [thread overview]
Message-ID: <8a4e4fa48aafa565da6eb7f2905d0a21be65901c.camel@amazon.com> (raw)
In-Reply-To: <5a80693d-87e3-26a5-0c80-fba7d0212260@citrix.com>
On Fri, 2020-02-21 at 13:02 +0000, Andrew Cooper wrote:
> On 21/02/2020 12:52, Xia, Hongyan wrote:
> > On Fri, 2020-02-21 at 11:50 +0000, Wei Liu wrote:
> > > Given that:
> > >
> > > 1. mapcache_domain is now a structure with only one member.
> > > 2. ents is a constant throughout domain's lifecycle.
> > >
> > > You can replace mapcache_domain with a boolean --
> > > mapcache_mapping_populated (?) in arch.pv.
> > >
> > > If I'm not mistaken, the size of the mapping is derived from the
> > > vcpu
> > > being initialised, so a further improvement is to lift the
> > > mapping
> > > creation out of mapcache_vcpu_init.
> >
> > But you can just XEN_DOMCTL_max_vcpus on a running domain to
> > increase
> > its max_vcpus count, so that ents is not constant?
>
> The comments suggest that, but it has never been implemented, and I'm
> in
> the process of purging the ability.
>
> Already now, max is passed into domain_create, and the
> XEN_DOMCTL_max_vcpus call has to exactly match what was passed to
> create. As soon as the {domain,vcpu}_destroy() functions become
> properly idempotent (so we can unwind from midway through after an
> -ENOMEM/etc), XEN_DOMCTL_max_vcpus will be dropped completely.
>
> d->max_cpus is set early during construction, and remains constant
> for
> the lifetime of the domain.
Thanks for the clarification. This simplifies things quite a bit.
Hongyan
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next prev parent reply other threads:[~2020-02-21 14:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-06 18:58 [Xen-devel] [PATCH v2] x86/domain_page: implement pure per-vCPU mapping infrastructure Hongyan Xia
2020-02-21 11:50 ` Wei Liu
2020-02-21 12:52 ` Xia, Hongyan
2020-02-21 13:02 ` Andrew Cooper
2020-02-21 14:40 ` Xia, Hongyan [this message]
2020-02-21 13:31 ` Jan Beulich
2020-02-21 14:36 ` Wei Liu
2020-02-21 14:55 ` Jan Beulich
2020-02-21 14:58 ` Wei Liu
2020-02-21 15:08 ` Jan Beulich
2020-02-21 14:52 ` Xia, Hongyan
2020-02-21 14:59 ` Jan Beulich
2020-02-21 14:39 ` Wei Liu
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