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DIR:OUT; SFP:1102; SCL:1; SRVR:DM5PR18MB2295; H:DM5PR18MB1499.namprd18.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; MX:1; A:1; received-spf: None (protection.outlook.com: suse.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: aUIjUVaR+yzfooJ6tlh5Z/to68YiGVkgARMQY80TNrLKaiUxS5linEhxgUb6SZnrTYRlCzVMX1V+hETNU67bsrWUjfT2FDn1sljFoa0aShG6A+KkcyJ800jXvCcsxW1clmxqTkEAvjUNlJIUagyXgLMct02tj4K58g56ZyG3DZ6uzfkwOzzLKYkTNCkSSBpjkOe84TSsKDIgtQDPAKkZyxj8EIkAFJ6e4qYwajeAaH7QFE5vfLDOUqF2x4JIHgbILn+hjCINwZgucvS6cy/ZizIBggj06qZKgCp8X53V5lehhnImvJSFcCTrvkS6VYOGmYKc87WtPxE9eyptMYaOWi7jYpZNrAz2Y2z1SwmFWK190W4iLmzGwkZPHy8G4erSFllGlHL5ukJ775R7FbtZav4e76BksRyUtsur8vwAoHM= MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 2a10d5f4-059d-4655-98eb-08d714550434 X-MS-Exchange-CrossTenant-originalarrivaltime: 29 Jul 2019 18:46:06.8783 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 856b813c-16e5-49a5-85ec-6f081e13b527 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: dfaggioli@suse.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR18MB2295 X-OriginatorOrg: suse.com Subject: Re: [Xen-devel] [RFC 0/6] XEN scheduling hardening X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: "sstabellini@kernel.org" , "andrii_anisov@epam.com" , "george.dunlap@eu.citrix.com" , "andrew.cooper3@citrix.com" , "tim@xen.org" , "julien.grall@arm.com" , Jan Beulich Content-Type: multipart/mixed; boundary="===============0525330695171406530==" Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" --===============0525330695171406530== Content-Language: en-US Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="=-mKJqG8u3hE9IDh0DoOOB" --=-mKJqG8u3hE9IDh0DoOOB Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2019-07-29 at 17:47 +0300, Andrii Anisov wrote: > On 26.07.19 15:14, Juergen Gross wrote: > > > >=20 > > Tasklets are sometimes used to perform async actions which can't be > > done > > in guest vcpu context. > > [...] > > Like switching a domain to shadow mode for L1TF > > mitigation, >=20 > Sorry I'm not really aware what L1TF mitigation is. > But >=20 > > or marshalling all cpus for stop_machine(). >=20 > I think I faced some time ago. When fixed a noticeable lag in video > playback at the moment of the other domain reboot. >=20 No, stop_machine() is not about a VM being shutdown/killed/stopped. It's, let's say, about all the (physical) CPU in the host having to do something, in a coordinated way. Check the comment in xen/include/xen/stop_machine.h > > You don't want > > to be able to block tasklets, you want them to run as soon as > > possible. >=20 > Should it really be done in the way of breaking scheduling? What if > the system has RT requirements? >=20 It's possible, I guess, that we can implement some of the things that are done in tasklets (either stop_machine() or something else) differently, and in a way that is less disruptive for scheduling and determinism. But, if it is, it's not going to be as easy as <>, I'm afraid. :-( Regards --=20 Dario Faggioli, Ph.D http://about.me/dario.faggioli Virtualization Software Engineer SUSE Labs, SUSE https://www.suse.com/ ------------------------------------------------------------------- <> (Raistlin Majere) --=-mKJqG8u3hE9IDh0DoOOB Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEES5ssOj3Vhr0WPnOLFkJ4iaW4c+4FAl0/PuwACgkQFkJ4iaW4 c+7Pxw//ati448hsuXPkBg0ZXY25z97+RqY+HdhqQKKIUE0WnEs/e9nN7fcgu3tW KUfNGoXdWS4PSokVT1nh40ByBVRXIuIXCIVMhzLsjWkHTg4c9beKpA7mzHvWrkAO Nk4JRFA3MibgJhxSu3rmyUsszmxMoH/N3tkshuQ5lVEnhiB6/KF0jFx2ighqo6m9 vonc2eblIrpzRohZjs7dbooMUq9gn+rqUJLPlNtDMvlDosgvcAOhrSAtWes5BUMA A3vo5tULR+alWGCSxp+M0QOOhf5w+C5s6JXVGaHqYkHZ36R6E3RKC7vK3keuJazY 99BU0cj8BfhiSUuN6fdtRYAWr+RyyO4fbfcqD/OKpAhr3Nx/glsg9suOCkNZmKsp QRj7PfommRdhH2MiEQslfWhOxYo0q9vY+5c+KWSeNsAn1OFkBn3fplcbJ5FV4pnC 6kgSNfDHRZDmRmqHjpwKphSoiDg/iNCcGiSULt7FNhFafbZUN3FpGDlJb8RRAb/w xS21AruKy/MrVlXAl+eWp+HmfdaaCYqfTSynqhC4HjontGy/EFH30wv/bA/zL+Na JBQ1+Y/Vgb2RKYKcuXEyd9d9qTBT7o5ow1MJhuDhwH3wjK9pXP+8vR9K/klF3X4S Cm0q+u0ncRkJqcwPpDpECsBinsuvWyysxrHd3Zw6KClX4KgqgxM= =dMEd -----END PGP SIGNATURE----- --=-mKJqG8u3hE9IDh0DoOOB-- --===============0525330695171406530== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVucHJvamVjdC5vcmcKaHR0cHM6Ly9saXN0 cy54ZW5wcm9qZWN0Lm9yZy9tYWlsbWFuL2xpc3RpbmZvL3hlbi1kZXZlbA== --===============0525330695171406530==--