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spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.44932.80375 (Exim 4.92) (envelope-from ) id 1klDkm-00048J-En; Fri, 04 Dec 2020 16:16:16 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 44932.80375; Fri, 04 Dec 2020 16:16:16 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1klDkm-00048C-Ac; Fri, 04 Dec 2020 16:16:16 +0000 Received: by outflank-mailman (input) for mailman id 44932; Fri, 04 Dec 2020 16:16:14 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1klDkk-000487-O7 for xen-devel@lists.xenproject.org; Fri, 04 Dec 2020 16:16:14 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id c8b1828c-dd67-46ec-a396-4132fbe838bf; Fri, 04 Dec 2020 16:16:13 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B9BB7ACC4; Fri, 4 Dec 2020 16:16:12 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: c8b1828c-dd67-46ec-a396-4132fbe838bf X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1607098572; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=8wHFCJcXLxaRCE//c8KZw/xWEWSTTcGqjK8EPcNdN4s=; b=hxvmS2q6N3Nl4P/4aNpN+Np+nJM7kvSudLfdsp1+kBLKZw0HT6BQ0wgEZ6tvzBPW6WHNw4 PobokZctW6TEOQB6ZEK3RpBP3nZBSEBXhlXAWcbph1TO6ie92yB1XEv0679P9AEqvStUp2 sMPU2HKyU5TeQdhQKEo8MGLMSUjlrWs= Subject: Re: [PATCH v2 05/17] xen/cpupool: switch cpupool list to normal list interface To: Dario Faggioli , Jan Beulich Cc: George Dunlap , xen-devel@lists.xenproject.org References: <20201201082128.15239-1-jgross@suse.com> <20201201082128.15239-6-jgross@suse.com> <54301d8c-2d69-3206-6c42-d2638b7e7aa3@suse.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <76e7d00f-b049-97fc-f9e2-ade76b10a93e@suse.com> Date: Fri, 4 Dec 2020 17:16:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Na8waiugEdiEkwE6AMBr4JLGmOuQAJmic" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --Na8waiugEdiEkwE6AMBr4JLGmOuQAJmic Content-Type: multipart/mixed; boundary="zZ5RQvfaEdQoknt99G5x3RkM1YvBQuudI"; protected-headers="v1" From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= To: Dario Faggioli , Jan Beulich Cc: George Dunlap , xen-devel@lists.xenproject.org Message-ID: <76e7d00f-b049-97fc-f9e2-ade76b10a93e@suse.com> Subject: Re: [PATCH v2 05/17] xen/cpupool: switch cpupool list to normal list interface References: <20201201082128.15239-1-jgross@suse.com> <20201201082128.15239-6-jgross@suse.com> <54301d8c-2d69-3206-6c42-d2638b7e7aa3@suse.com> In-Reply-To: --zZ5RQvfaEdQoknt99G5x3RkM1YvBQuudI Content-Type: multipart/mixed; boundary="------------38956755D0F484510DE165D9" Content-Language: en-US This is a multi-part message in MIME format. --------------38956755D0F484510DE165D9 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 04.12.20 17:13, Dario Faggioli wrote: > On Tue, 2020-12-01 at 10:18 +0100, J=C3=BCrgen Gro=C3=9F wrote: >> On 01.12.20 10:12, Jan Beulich wrote: >>> What guarantees that you managed to find an unused ID, other >>> than at current CPU speeds it taking too long to create 4 >>> billion pools? Since you're doing this under lock, wouldn't >>> it help anyway to have a global helper variable pointing at >>> the lowest pool followed by an unused ID? >> >> An admin doing that would be quite crazy and wouldn't deserve better. >> >> For being usable a cpupool needs to have a cpu assigned to it. And I >> don't think we are coming even close to 4 billion supported cpus. :-) >> >> Yes, it would be possible to create 4 billion empty cpupools, but for >> what purpose? There are simpler ways to make the system unusable with >> dom0 root access. >> > Yes, I agree. I don't think it's worth going through too much effort > for trying to deal with that. >=20 > What I'd do is: > - add a comment here, explaining quickly exactly this fact, i.e., > that it's not that we've forgotten to deal with this and it's all > on=C2=A0purpose. Actually, it can be either a comment here or it ca= n be > mentioned in the changelog. I'm fine either way > - if we're concerned about someone doing: > for i=3D1...N { xl cpupool-create foo bar } > with N ending up being some giant number, e.g., by mistake, I don't= > think it's unreasonable to come up with an high enough (but > certainly not in the billions!) MAX_CPUPOOLS, and stop creating new= > ones when we reach that level. Do you agree that this could be another patch? I'm not introducing that (theoretical) problem here. 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