From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99BE6C433E0 for ; Fri, 19 Jun 2020 01:02:42 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6384420771 for ; Fri, 19 Jun 2020 01:02:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.b="GseJdLHh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6384420771 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:53350 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jm5QX-0003O6-LK for qemu-devel@archiver.kernel.org; Thu, 18 Jun 2020 21:02:41 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58538) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jm5PZ-0002J8-QQ; Thu, 18 Jun 2020 21:01:41 -0400 Received: from bilbo.ozlabs.org ([2401:3900:2:1::2]:58341 helo=ozlabs.org) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jm5PV-0007hN-UV; Thu, 18 Jun 2020 21:01:41 -0400 Received: by ozlabs.org (Postfix, from userid 1007) id 49p0qv1Sgtz9sDX; Fri, 19 Jun 2020 11:01:31 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1592528491; bh=tx0r9aF6bHVTYyJWgJCBQuxygcvmWgiZiJS5B4hROZ0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GseJdLHhyS/D3LTe7STDbU76+BQzei5692ei90VtnvS8RWBTz5p5WyrE+AJOSz2lr MDyuYpO9beg1WETPbISMubcxannkDc9heIPS50DzhZoie4eNUr68r2YSblLCBUShPQ OV4FiAm4/9CTnnccS4N+nkSzkjxnkodjJ8M1noXA= Date: Fri, 19 Jun 2020 11:01:22 +1000 From: David Gibson To: Halil Pasic Subject: Re: [PATCH v2 1/1] virtio-ccw: auto-manage VIRTIO_F_IOMMU_PLATFORM if PV Message-ID: <20200619010122.GH17085@umbus.fritz.box> References: <20200514221155.32079-1-pasic@linux.ibm.com> <20200520121507-mutt-send-email-mst@kernel.org> <20200606013217.2cffa3ed.pasic@linux.ibm.com> <20200608181428.3c6f127c.cohuck@redhat.com> <20200608190045.319dd68b.pasic@linux.ibm.com> <20200609084402.35d317ec.cohuck@redhat.com> <20200610042554.GD494336@umbus.fritz.box> <20200610233714.05174c93.pasic@linux.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wayzTnRSUXKNfBqd" Content-Disposition: inline In-Reply-To: <20200610233714.05174c93.pasic@linux.ibm.com> Received-SPF: pass client-ip=2401:3900:2:1::2; envelope-from=dgibson@ozlabs.org; helo=ozlabs.org X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -9 X-Spam_score: -1.0 X-Spam_bar: - X-Spam_report: (-1.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HEADER_FROM_DIFFERENT_DOMAINS=1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , Boris Fiuczynski , Janosch Frank , Pierre Morel , "Michael S. Tsirkin" , Cornelia Huck , David Hildenbrand , qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org, Viktor Mihajlovski , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --wayzTnRSUXKNfBqd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 10, 2020 at 11:37:14PM +0200, Halil Pasic wrote: > On Wed, 10 Jun 2020 14:25:54 +1000 > David Gibson wrote: >=20 > > > > I'm going to definitely have a good look at that. What I think spec= ial > > > > about s390 is that F_ACCESS_PLATFORM is hurting us because all IO n= eeds > > > > to go through ZONE_DMA (this is a problem of the implementation that > > > > stemming form a limitation of the DMA API, upstream didn't let me > > > > fix it). =20 > > >=20 > > > My understanding is that power runs into similar issues, but I don't > > > know much about power, so I might be entirely wrong :) =20 > >=20 > > Sort of, but not to the same extent, I think. >=20 > I'm curious what are the ramifications of a misguided hotplug on POWER? > Does using F_ACCESS_PLATFORM when it isn't required have any > significant drawbacks, or are you fine to just go with the safe option? I expect it will have some performance impact, though it shouldn't be *that* bad, at least if your guest kernel is ddw / large IOMMU window capable. Changing the default would require a machine type version bump, of course. --=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 --wayzTnRSUXKNfBqd Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAl7sDmIACgkQbDjKyiDZ s5LzphAAjmB4ZOjj8SQ9Mftxq18eNoUdaFrNO/AU0Xhict72ejnWHW7YzXuU1uGN N2mt3e8b3Q7WUivkN2m3SHesxojS45Fv5T1m3weWEUwYemkM+zrLbelfCf8Li6TO p0Nyjk1mhXcYJHI3NaOIekKCHtCPnoJqb4qKa5ENNwIoxWmvgcy6ZOW2/roXSX0T yOTJWtr+W1V6rWUYykpr2f63eF6IA6vFulyDafNz2G+V3nI02UtNs2E9Y2Oe05Fe WEMTLTKsreYNiX9HaNGeI2Fy2NHBsc7FKD7jmAihBsKhX9OgNHY77uO2mpclTrRX 6sfkVEAaj3r2mOh5Rm622zHzpeED9Co5xnB27RvXOJ9gLSS5sooh0zWnAHb6Y3WP cRkhagt8J85QobkJcxiocOtJYbcK3WQJ6ouwXemlSezEECZeuMK1Uw36l763ick2 cMgNl7XBL2P31dVXIsf0pLF/ys8NEJix1IIOHv+5gA+8gQbbVg1OLEUIVMxvqQQS 09lW/V6d3+4lbxikn234CoIzBHV0EsQnJ7ViRGEWA6j7RUnSATsRuXvDKHE+Ytmp 1Pq/0Svup2EBfeHosAEOkinFOkG6eFThII1wo6nJr4FtO/MMfCC9aSjIq/5xGlqT +8ACj2wSwKZ2uPJryJ0liW2gGTT02QDGUtRiSmBz1Wl+qonL+mU= =CoWe -----END PGP SIGNATURE----- --wayzTnRSUXKNfBqd--