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=-13.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 29617C33CA2 for ; Fri, 10 Jan 2020 08:56:23 +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 E26C42072A for ; Fri, 10 Jan 2020 08:56:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E26C42072A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42692 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipq5e-0001mF-2D for qemu-devel@archiver.kernel.org; Fri, 10 Jan 2020 03:56:22 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47262) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipq4g-000126-Sw for qemu-devel@nongnu.org; Fri, 10 Jan 2020 03:55:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ipq4d-00077m-RB for qemu-devel@nongnu.org; Fri, 10 Jan 2020 03:55:22 -0500 Received: from 6.mo5.mail-out.ovh.net ([178.32.119.138]:37822) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ipq4d-0006og-7D for qemu-devel@nongnu.org; Fri, 10 Jan 2020 03:55:19 -0500 Received: from player714.ha.ovh.net (unknown [10.108.57.38]) by mo5.mail-out.ovh.net (Postfix) with ESMTP id 1DEF6266734 for ; Fri, 10 Jan 2020 09:55:07 +0100 (CET) Received: from kaod.org (lns-bzn-46-82-253-208-248.adsl.proxad.net [82.253.208.248]) (Authenticated sender: groug@kaod.org) by player714.ha.ovh.net (Postfix) with ESMTPSA id 2CE56DFE6775; Fri, 10 Jan 2020 08:55:04 +0000 (UTC) Date: Fri, 10 Jan 2020 09:55:02 +0100 From: Greg Kurz To: =?UTF-8?B?QW5kcsOp?= Silva Subject: Re: [PATCH] virtio: Prevent double swap due to target pre 1.0 VirtIO Message-ID: <20200110095502.4635f34c@bahia.lan> In-Reply-To: References: <20200108161618.221116-1-afscoelho@gmail.com> <20200109054233-mutt-send-email-mst@kernel.org> <20200109073529-mutt-send-email-mst@kernel.org> <20200109170640.4c3fa148@bahia.lan> X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Ovh-Tracer-Id: 4317263196199754187 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedufedrvdeivddguddulecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvuffkjghfofggtgfgsehtqhertdertdejnecuhfhrohhmpefirhgvghcumfhurhiiuceoghhrohhugheskhgrohgurdhorhhgqeenucffohhmrghinhepohhpvghnshhouhhrtggvrdhorhhgpdhqvghmuhdrohhrghenucfkpheptddrtddrtddrtddpkedvrddvheefrddvtdekrddvgeeknecurfgrrhgrmhepmhhouggvpehsmhhtphdqohhuthdphhgvlhhopehplhgrhigvrhejudegrdhhrgdrohhvhhdrnhgvthdpihhnvghtpedtrddtrddtrddtpdhmrghilhhfrhhomhepghhrohhugheskhgrohgurdhorhhgpdhrtghpthhtohepqhgvmhhuqdguvghvvghlsehnohhnghhnuhdrohhrghenucevlhhushhtvghrufhiiigvpedt X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 178.32.119.138 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: QEMU Developers , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 9 Jan 2020 18:18:57 -0300 Andr=C3=A9 Silva wrote: > Hi Greg, >=20 Hi Andr=C3=A9, > Thanks for the commit info. > But I'm testing in this scenario, that is, a ppc64le host with a ppc64 > BE guest, and without my patch I can't get virtio to work. The patch What are the symptoms without your patch ? What's the QEMU version ? > makes virtio 0.95 (legacy) net, scsi, blk work. I don't get the > firmware error. I also tested with a ppc64le guest and had no problems > either. Maybe we have different firmware versions? >=20 > My firmware output: >=20 > SLOF ********************************************************************= ** > QEMU Starting > Build Date =3D Jul 3 2019 12:26:14 > FW Version =3D git-ba1ab360eebe6338 I'm using the latest SLOF from the QEMU tree (pc-bios/slof.bin): SLOF ********************************************************************** QEMU Starting Build Date =3D Dec 17 2019 11:31:13 FW Version =3D git-9546892a80d5a4c7 Do you hit the issue with upstream QEMU ? > Press "s" to enter Open Firmware. >=20 > Populating /vdevice methods > Populating /vdevice/vty@71000000 > Populating /vdevice/nvram@71000001 > Populating /vdevice/v-scsi@71000002 > SCSI: Looking for devices > 8200000000000000 CD-ROM : "QEMU QEMU CD-ROM 2.5+" > Populating /pci@800000020000000 > 00 0000 (D) : 1af4 1000 virtio [ net ] > 00 0800 (D) : 1af4 1001 virtio [ block ] > No NVRAM common partition, re-initializing... > Scanning USB > Using default console: /vdevice/vty@71000000 >=20 > Welcome to Open Firmware >=20 > Copyright (c) 2004, 2017 IBM Corporation All rights reserved. > This program and the accompanying materials are made available > under the terms of the BSD License available at > http://www.opensource.org/licenses/bsd-license.php >=20 >=20 > Trying to load: from: /pci@800000020000000/scsi@1 ... Successfully loa= ded >=20 > >> FreeBSD/powerpc Open Firmware boot block > Boot path: /pci@800000020000000/scsi@1 > Boot loader: /boot/loader > Boot volume: /pci@800000020000000/scsi@1:2 > Consoles: Open Firmware console >=20 > FreeBSD/powerpc64 Open Firmware loader, Revision 0.1 > (Mon Nov 11 22:33:43 -02 2019 jenkins@FreeBSD_x86) > Memory: 4194304KB > Booted from: /pci@800000020000000/scsi@1 >=20 > Loading /boot/defaults/loader.conf > /boot/kernel/kernel data=3D0x129f658+0x4aaa88 syms=3D[0x8+0x105120+0x8+0x= 125429] > ... >=20 > Until now, I was able to test the patch and see virtio working on the > following systems: >=20 > Qemu Host Guest Guest VirtIO > -------- ---------------- ------------------------------- -------------- > master Ubuntu ppc64le FreeBSD 13.0-current ppc64 BE legacy > master Ubuntu ppc64le debian 4.19.0-6-powerpc64le modern > master Ubuntu ppc64le debian 4.19.0-6-powerpc64le legacy > master arch x86_64 FreeBSD 13.0-current ppc64 BE legacy >=20 > Thanks, > andr=C3=A9 >=20 > On Thu, Jan 9, 2020 at 1:06 PM Greg Kurz wrote: > > > > On Thu, 9 Jan 2020 07:39:17 -0500 > > "Michael S. Tsirkin" wrote: > > > > > On Thu, Jan 09, 2020 at 09:25:42AM -0300, Andr=C3=A9 Silva wrote: > > > > Hi Michael! > > > > Thanks for reviewing the patch! > > > > > > > > > we always get LE values from memory subsystem, > > > > > not target endian values: > > > > > > > > I see. So do you think the patch is correct in eliminating the extra > > > > swap (as virtio_config_readw for example already makes a swap)? > > > > > > > > Thanks, > > > > andr=C3=A9 > > > > > > I don't think it is, I think we do need an extra swap > > > in some cases. It's possible that some cross-endian > > > setups are broken now, if so pls include testing > > > result not just theoretical analysis. > > > > > > > I confirm that we must keep the extra swap otherwise > > read/write in cross-endian setups will have wrong > > endian. Please read this commit for a more detailed > > explanation: > > > > commit 82afa58641b0e67abbaf4da6c325ebd7c2513262 > > Author: Benjamin Herrenschmidt > > Date: Tue Jan 10 01:35:11 2012 +0000 > > > > virtio-pci: Fix endianness of virtio config > > > > https://git.qemu.org/?p=3Dqemu.git;a=3Dcommitdiff;h=3D82afa58641b0e67ab= baf4da6c325ebd7c2513262 > > > > This is especially critical on ppc64 since _all_ hosts are now LE > > but the first piece of code in the guest that is likely to drive > > the device is the SLOF firmware which is BE. > > > > This is what we get with this patch when trying to run a pseries guest = on a > > ppc64le host: > > > > Trying to load: from: /pci@800000020000000/scsi@0 ... virtioblk_transf= er: Access beyond end of device! > > > > Cheers, > > > > -- > > Greg > > > > > > On Thu, Jan 9, 2020 at 7:50 AM Michael S. Tsirkin = wrote: > > > > > > > > > > On Wed, Jan 08, 2020 at 01:16:18PM -0300, Andre Silva wrote: > > > > > > Remove the bswap function calls after reading and before writing > > > > > > memory bytes in virtio_pci_config_read and virtio_pci_config_wr= ite > > > > > > because they are reverting back an already swapped bytes. > > > > > > > > > > > > Consider the table below in the context of virtio_pci_config_re= ad > > > > > > function. > > > > > > > > > > > > Host Target virtio-config-read[wl] > > > > > > swap? virtio-is-big-endian? = extra bswap? Should be Final result Final result ok? > > > > > > ----- ------- ------------------------ ----------------------- = -------------- ----------- -------------- ------------------ > > > > > > LE BE s(x) true = s(s(x)) s(x) x No > > > > > > LE LE x false = - x x Yes > > > > > > BE LE s(x) false = - s(x) s(x) Yes > > > > > > BE BE x true = s(x) x s(x) No > > > > > > > > > > we always get LE values from memory subsystem, > > > > > not target endian values: > > > > > > > > > > static const MemoryRegionOps virtio_pci_config_ops =3D { > > > > > .read =3D virtio_pci_config_read, > > > > > .write =3D virtio_pci_config_write, > > > > > .impl =3D { > > > > > .min_access_size =3D 1, > > > > > .max_access_size =3D 4, > > > > > }, > > > > > .endianness =3D DEVICE_LITTLE_ENDIAN, > > > > > }; > > > > > > > > > > > > > > > This triggers another swap in address_space_ldl_internal > > > > > (memory_ldst.inc.c). > > > > > > > > > > > > > > > > In table above, when target is big endian and VirtIO is pre 1.0, > > > > > > function virtio_is_big_endian would return true and the extra > > > > > > swap would be executed, reverting the previous swap made by > > > > > > virtio_config_read[wl]. > > > > > > > > > > > > The 's(x)' means that a swap function was applied at > > > > > > address x. 'LE' is little endian and 'BE' is big endian. The > > > > > > 'Final result' column is the returned value from > > > > > > virtio_pci_config_read, considering a target Virtio pre 1.0. > > > > > > 'x' means that target's value was not swapped in Qemu, 's(x)' m= eans > > > > > > that Qemu will use a swapped value. > > > > > > > > > > > > If we remove the extra swap made in virtio_pci_config_read we w= ill > > > > > > have the correct result in any host/target combination, both for > > > > > > VirtIO pre 1.0 or later versions. > > > > > > > > > > > > The same reasoning applies to virtio_pci_config_write. > > > > > > > > > > > > Signed-off-by: Andre Silva > > > > > > --- > > > > > > hw/virtio/virtio-pci.c | 12 ------------ > > > > > > 1 file changed, 12 deletions(-) > > > > > > > > > > > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > > > > > > index c6b47a9c73..4ba9e847f3 100644 > > > > > > --- a/hw/virtio/virtio-pci.c > > > > > > +++ b/hw/virtio/virtio-pci.c > > > > > > @@ -431,15 +431,9 @@ static uint64_t virtio_pci_config_read(voi= d *opaque, hwaddr addr, > > > > > > break; > > > > > > case 2: > > > > > > val =3D virtio_config_readw(vdev, addr); > > > > > > - if (virtio_is_big_endian(vdev)) { > > > > > > - val =3D bswap16(val); > > > > > > - } > > > > > > break; > > > > > > case 4: > > > > > > val =3D virtio_config_readl(vdev, addr); > > > > > > - if (virtio_is_big_endian(vdev)) { > > > > > > - val =3D bswap32(val); > > > > > > - } > > > > > > break; > > > > > > } > > > > > > return val; > > > > > > @@ -465,15 +459,9 @@ static void virtio_pci_config_write(void *= opaque, hwaddr addr, > > > > > > virtio_config_writeb(vdev, addr, val); > > > > > > break; > > > > > > case 2: > > > > > > - if (virtio_is_big_endian(vdev)) { > > > > > > - val =3D bswap16(val); > > > > > > - } > > > > > > virtio_config_writew(vdev, addr, val); > > > > > > break; > > > > > > case 4: > > > > > > - if (virtio_is_big_endian(vdev)) { > > > > > > - val =3D bswap32(val); > > > > > > - } > > > > > > virtio_config_writel(vdev, addr, val); > > > > > > break; > > > > > > } > > > > > > -- > > > > > > 2.24.1 > > > > > > > > > > > > >