From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33737) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f5kug-0006XW-2D for qemu-devel@nongnu.org; Tue, 10 Apr 2018 00:29:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f5kuc-0003tR-Vb for qemu-devel@nongnu.org; Tue, 10 Apr 2018 00:29:46 -0400 Date: Tue, 10 Apr 2018 14:23:55 +1000 From: David Gibson Message-ID: <20180410042355.GH3361@umbus.fritz.box> References: <1522938923-96058-1-git-send-email-spopovyc@redhat.com> <1522938923-96058-2-git-send-email-spopovyc@redhat.com> <20180406035249.GA10482@in.ibm.com> <1d1893fc-1484-86e0-ed1b-f9cf7b35fbb5@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="cfJ13FhsvNR/yOpm" Content-Disposition: inline In-Reply-To: <1d1893fc-1484-86e0-ed1b-f9cf7b35fbb5@redhat.com> Subject: Re: [Qemu-devel] [PATCH for 2.13 1/2] Revert "spapr: Don't allow memory hotplug to memory less nodes" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Serhii Popovych Cc: bharata@linux.vnet.ibm.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org --cfJ13FhsvNR/yOpm Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Apr 06, 2018 at 08:48:55AM +0300, Serhii Popovych wrote: > Bharata B Rao wrote: > > On Thu, Apr 05, 2018 at 10:35:22AM -0400, Serhii Popovych wrote: > >> This reverts commit b556854bd8524c26b8be98ab1bfdf0826831e793. > >> > >> Leave change @node type from uint32_t to to int from reverted commit > >> because node < 0 is always false. > >> > >> Signed-off-by: Serhii Popovych > >> --- > >> hw/ppc/spapr.c | 22 ---------------------- > >> 1 file changed, 22 deletions(-) > >> > >> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > >> index 2c0be8c..3ad4545 100644 > >> --- a/hw/ppc/spapr.c > >> +++ b/hw/ppc/spapr.c > >> @@ -3477,28 +3477,6 @@ static void spapr_machine_device_plug(HotplugHa= ndler *hotplug_dev, > >> return; > >> } > >> > >> - /* > >> - * Currently PowerPC kernel doesn't allow hot-adding memory to > >> - * memory-less node, but instead will silently add the memory > >> - * to the first node that has some memory. This causes two > >> - * unexpected behaviours for the user. > >> - * > >> - * - Memory gets hotplugged to a different node than what the= user > >> - * specified. > >> - * - Since pc-dimm subsystem in QEMU still thinks that memory= belongs > >> - * to memory-less node, a reboot will set things accordingly > >> - * and the previously hotplugged memory now ends in the rig= ht node. > >> - * This appears as if some memory moved from one node to an= other. > >> - * > >> - * So until kernel starts supporting memory hotplug to memory= -less > >> - * nodes, just prevent such attempts upfront in QEMU. > >> - */ > >> - if (nb_numa_nodes && !numa_info[node].node_mem) { > >> - error_setg(errp, "Can't hotplug memory to memory-less nod= e %d", > >> - node); > >> - return; > >> - } > >> - > >=20 > > If you remove this unconditionally, wouldn't it be a problem in case > > of newer QEMU with older guest kernels ? >=20 > Yes, that definitely would affect guest kernels without such support. We > probably need to add some capability to test for guest kernel > functionality presence. Hm, maybe. So first, we should check when the guest side support came in. If it's old enough we might not care. PAPR does include a mechanism for negotiating guest/host capabilities. However, I don't think it has a bit for this specific feature, so I can't really see a way to do this cleanly. I don't think we necessarily have to handle that case: it's not like we can reasonably workaround *every* possible guest bug/limitation =66rom the host side. If you want to create a system with a memory-less node you need an OS that can handle that, nothing really special there. --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --cfJ13FhsvNR/yOpm Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAlrMPFsACgkQbDjKyiDZ s5JR0xAAuv3NjUp1trvpBCNPzFNQJKFw9yVbPfyUbDxVDMqCFme4NknrNgvUPfWJ nKpXaxvSLdtwGCMH1AkHyv6iFoIIBcj4Ea9NUdGilyiueTXUiyWpLxCJ/pZnnDMu 0aSR1oPYrOWK+7WIO5ldiphmaDN0sTQ+Ed42kDLGxCTynsiLnRy6BUM5m8PhS01h Dc8eWgH5Miz6QyAj54kdH3WFJa5xqAkyutiJLYTKFXlxB9TGRPbtZHuAX9t0d7vG CUS3+fGEAbo+UEIAsn0wn7b7CJ2biDsLw+BngacPlaQw/EvrBm+MM8XLnxxftzWQ Q7XWbiE4z9JmgI82FXUjoc2Xu46mSwpbjq1M8krGnLbvWRJKCH5XxWGoJaU90ccQ sMr5rksP8DwPfGsHJi8jetkbx5ka+iKqCS45uPrDHBO3tMfBA/sPfpTnuPKJCQ9r drvzxTG31OwyGR3Jk7S3va3EzKXC7+HGTad2Rdn7FYJVosK+55WL1tWbMsTPTaWX t8XhOwD2wkhSdShKIPUyOXEB8YNHZewSxz2gddUruK/TFF2DzKXXXG3fQrWyrYv9 mE0DUqP9pywGvdiN4ey2jGThEhLt3ubPs8145tzMWqHXmcWTISw2d2sfBp65KfkC 7fQBAxbj8ndT6XsvLHOXiawbPpB9zaSbd/ltQf02rKCbJ/Mpj10= =jH1R -----END PGP SIGNATURE----- --cfJ13FhsvNR/yOpm--