From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [PATCH v3 10/10] xen/arm: Enable errata for secondary CPU on hotplug after the boot Date: Thu, 10 May 2018 18:21:57 +0200 Message-ID: <7eb8af10b99b61720ecd9ff273b38ec1e4ae163d.camel@suse.com> References: <20180427171258.28852-1-mirela.simonovic@aggios.com> <20180427171258.28852-11-mirela.simonovic@aggios.com> <4dec77ef3b2a940453e1bc112e6dae21cb99af18.camel@suse.com> <300e3466-8214-764a-6c33-ce8aaea31ed9@arm.com> <16d143e7-9edc-830d-8688-74839cb11583@arm.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3367610054844486687==" Return-path: In-Reply-To: <16d143e7-9edc-830d-8688-74839cb11583@arm.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" To: Julien Grall , Mirela Simonovic Cc: "Edgar E. Iglesias" , Stefano Stabellini , Davorin Mista , Xen Devel List-Id: xen-devel@lists.xenproject.org --===============3367610054844486687== Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-RAUAzQGqctzeAnl2Ids5" --=-RAUAzQGqctzeAnl2Ids5 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2018-05-10 at 17:02 +0100, Julien Grall wrote: > On 10/05/18 16:49, Mirela Simonovic wrote: > > Regardless of the fact that the notifier returns an error or not, I > > believe it would be good and safe to set priority and document that > > priority zero would cause racing issue in the scenario I debugged > > today. I'm pretty sure that this discussion would be forgotten soon > > and it really should be documented in code/comment. > >=20 > > In emails above I assumed we'll stop the erroneous CPU. I didn't > > have > > a chance to try returning an error until few minutes ago. > > I tried returning an error from the notifier now and the whole > > system > > fails. You realized according to the answer below that this is > > going > > to happen. >=20 > I was aware about it since the beginning. The whole point of the=20 > conversation was we should avoid to take the decision at the lower > level=20 > and let the upper layer decide what to do. >=20 This makes sense to me. > > I would rather stop CPU because changing notify_cpu_starting > > affects > > x86 as well, I cannot dig into that and it would be really to much > > for > > this series. Since you're fine with stopping cpu as well, please > > lets > > do that instead of escalating this to who knows where :) >=20 > Also, while I suggest that it could be replaced by stop_cpu() in the=20 > common code, I also suggested that notifier_cpu_starting() could > return=20 > an error then the architecture specific code can decide what to do. >=20 > On x86 it would still be a BUG_ON(notifier_cpu_starting()). On Arm > we=20 > can decide what to do. But it is not part of that discussion here. >=20 As just saind in the other email, I don't think this is all it's necessary to enable CPU_STARTING to fail. Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Software Engineer @ SUSE https://www.suse.com/ --=-RAUAzQGqctzeAnl2Ids5 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+4FAlr0caUACgkQFkJ4iaW4 c+6h+A//ZamWGgG+LePfMOeVKoW+7kqHqlGH5luqZfHhKLUK/n5XTJ4E9QbAP/CN mbywlTmkiPFZyj0+INPDZjdyKMYCoU1tw81m2BXIllJMKfpq5BhbhjyuV2uiMPMf /sU+3dIeKyXYyZwrbyo9mhus6as4589ZEPmj38+3wzSMKpTqr9aWsMf6y1TcPCzn 2fayMmiHzrCqxKChlI+oFCynRZl0LktIR2WHmYbgmHXV516Mu8vNs/EnzMY33aEf bDcCQMkvdQEXHvSC2dJoLh0tTzHzYDGpvreGNqpYRBrJ83ST4WmmL0hnmCxbxgUL /qFZu15PEOyWTjGSGKmd3ZhIgDz1kULJU/w233hVbgkewo2RB90AFYV1KCrrEGJm SY5z973AdH5R1Ikl2tuHyCv6BnHjKvQIZE/f3k3ityvqb1V/4L0iy6lZeRllHXFD TJHJ60dVpnoD6RICvy1f+wBYtIeaoDYOfc7yyRXV0uNQyYpA99sPhEt2rjSVM4X7 Z415De/SdaS2CKdMlKbDYIVYnmni+CXG92Es2xfZhr8AnOB1AMwjo6V/RHTX6jRS 1h6q50TDZpRtJ+Ok5Hwv380ZJIcatScRnUYyLoN+s5aZTLmhmWeQWqHA5Ql/7K7a +71yQEbXx7i966zE9THCZaLwGAuqZFLay/RYnGwatLwDcf+59ew= =wZZF -----END PGP SIGNATURE----- --=-RAUAzQGqctzeAnl2Ids5-- --===============3367610054844486687== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVucHJvamVjdC5vcmcKaHR0cHM6Ly9saXN0 cy54ZW5wcm9qZWN0Lm9yZy9tYWlsbWFuL2xpc3RpbmZvL3hlbi1kZXZlbA== --===============3367610054844486687==--