From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [RFC 0/5] xen/arm: support big.little SoC Date: Thu, 22 Sep 2016 18:31:46 +0200 Message-ID: <1474561906.4393.395.camel@citrix.com> References: <20160919083619.GA16854@linux-7smt.suse> <97d77bdb-2f4e-e89a-95b9-8aacb56eebc0@suse.com> <1474305482.4393.42.camel@citrix.com> <1474325742.4393.78.camel@citrix.com> <1474332846.4393.153.camel@citrix.com> <20160920100331.GB8084@linux-u7w5.ap.freescale.net> <4c52141f-a6a4-a0b1-dced-f799b592481e@arm.com> <61196660-df7c-7324-2fb6-cfb11f44ea1e@arm.com> <39623498-bb30-4ff7-f075-219487a5afbb@arm.com> <6bd7d587-f9ba-c3bf-db96-46a2958d9e5b@arm.com> <1474472740.4393.281.camel@citrix.com> <75979980-985e-51c8-9331-ad9657e4d612@arm.com> <1474533783.4393.312.camel@citrix.com> <7b87557d-39ee-0b1d-7163-00317571569f@arm.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============8457924030255608793==" Return-path: In-Reply-To: <7b87557d-39ee-0b1d-7163-00317571569f@arm.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" To: Julien Grall , George Dunlap , Stefano Stabellini Cc: Juergen Gross , Peng Fan , Steve Capper , George Dunlap , Andrew Cooper , Punit Agrawal , "xen-devel@lists.xen.org" , Jan Beulich , Peng Fan List-Id: xen-devel@lists.xenproject.org --===============8457924030255608793== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="=-RO8LkeTrLu1TD2aHvfAH" --=-RO8LkeTrLu1TD2aHvfAH Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2016-09-22 at 12:24 +0100, Julien Grall wrote: > On 22/09/16 09:43, Dario Faggioli wrote: > > Local migration basically --from the vcpu perspective-- means > > create a > > new vcpu, stop the original vcpu, copy the state from original to > > new, > > destroy the original vcpu and start the new one. My point is that > > this > > is not something that can be done within nor initiated by the > > scheduler, e.g., during a context switch or a vcpu wakeup! >=20 > By local migration, I meant from the perspective of the hypervisor. > In=C2=A0 > the hypervisor you have to trap feature registers and other=C2=A0 > implementation defined registers to show the same value across all > the=C2=A0 > physical CPUs. >=20 You mean we trap feature registers during the (normal) execution of a vcpu, because we want Xen to vet what's returned to the guest itself. And that migration support, and hence the possibility that the guest have been migrated to a cpu different than the one where it was created, is already one of the reasons why this is necessary... right? If yes, and if that's "all" we need, I think it should be fine. > You don't need to recreate the vCPU every time you move from one set > of=C2=A0 > CPUs to another one. Sorry for the confusion. >=20 No, I am sorry... it's not you that you're making confusion, it's probably me knowing to few about ARM, and did not think at the above when you said "migration". :-) Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-RO8LkeTrLu1TD2aHvfAH Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCAAGBQJX5AdyAAoJEBZCeImluHPuVOMP/1I2JYPPSsPjFvFwO9DXcfum hhjsFzYa+RnED73cS1FHhXq/lj8+1CmlItgBDpUa+x0orhBgOW2Nh8qODPovYWSb g/w7haEOSBGouwVoOdYgRT8Tq+ulWmrdBzQmJyO8eRTfVcTF8erw9/rEsRuLX5Up Nzqwhr+TYmIYlQJ+yK6hfSznzpd9SjH3kjjtGre8SfGloBi3V+D935M+PNU571zw wcC1V3N5B+3UE6Jxx86nd33yDahlpywGEy2mZ3ILGURGQcXGxA66GVBeoOrgh5jJ ylQ9LlQHBKc+cbHHECy8hxasX/gibc9lIuanmGDZKbS7JDx/vffhWm2EbEiwhFVe sR4Fy4CXURF5D6MCWl0WCiG7BN9auaJg9TuOGFdL6FW7rRnkR8BSK2YTd9gI+ceT k8LsV+ocnkIoUfaqhFvjbFAMIUfBBnYHC92crxlLPaP0miJEXVc9VlZJcvv/Wfs8 BIpgL91vVUZNKcaBUd8WETCRouGX2miypGGWJHFrPcbcXhQq0KOVrzkeghMG9y2D 2E5c5JwIJBbGlKKvEquUXB+ywyjbvgajaEL8KhZmQHGH0ETSiD/ZYTewBeQEOfxJ dX8PHqAV76FaF3y8sz+c78N53xjvnTFpdqHp9TOqkUMIK47ewEG++ldfYtFnkqq7 GJECX3SHMdJ1Vy4UTzZa =Nx0I -----END PGP SIGNATURE----- --=-RO8LkeTrLu1TD2aHvfAH-- --===============8457924030255608793== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVuLm9yZwpodHRwczovL2xpc3RzLnhlbi5v cmcveGVuLWRldmVsCg== --===============8457924030255608793==--