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=-9.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 E1FA6C282DD for ; Wed, 8 Jan 2020 13:45:21 +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 AF8B2206DB for ; Wed, 8 Jan 2020 13:45:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RJo/CU7K" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF8B2206DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:44130 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipBeC-00083D-Gz for qemu-devel@archiver.kernel.org; Wed, 08 Jan 2020 08:45:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47393) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipAu6-0005iM-NH for qemu-devel@nongnu.org; Wed, 08 Jan 2020 07:57:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ipAu5-0006u4-LR for qemu-devel@nongnu.org; Wed, 08 Jan 2020 07:57:42 -0500 Received: from mail-qt1-x841.google.com ([2607:f8b0:4864:20::841]:45167) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ipAu5-0006sH-HY for qemu-devel@nongnu.org; Wed, 08 Jan 2020 07:57:41 -0500 Received: by mail-qt1-x841.google.com with SMTP id w30so1466077qtd.12 for ; Wed, 08 Jan 2020 04:57:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=BJ2O4PQRw1ys8DhPlVU2A3mHoRVTkwiCzLu+4EEMMFE=; b=RJo/CU7KPmVK+yVU3Isg+LDmVAPnLwoua90zVWOWLiyTBLzMEO6i7GlnFKVKLDSwQB 6gGib2whmemSzZXmGIf2lAPKhKRWxls4VMf/E/CNSBnecgMtQt/Z3Hnzow3Llieek3Rn W1m+Jip+25Ne564NXnUV7ff+XQA7zNcDOUDMl1pJrwohrntmtH3hzpe3BiFzAXx5slPY XpLq2HTYbdudsSCkI+H2VwxmiKvt3W3WoX3MNjn1lsIgNtdQP73herNXqRK+Xl2n+NMZ hwM29A4m5z2BXcp/kJN9AC8KSwPSKmNA9hufJkcFGU1brqRvSZsP+JWxrJE1CdcRKgxf Lt0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=BJ2O4PQRw1ys8DhPlVU2A3mHoRVTkwiCzLu+4EEMMFE=; b=aV0kC4FXyfKoSze5sthgPUjqWk5/mIRWj2uZBjDfMpqp+ErJEi9JiV+S6s4rgej3u6 cqSvrw/h2EnBvaebAwCx/B8bhGO5mhraN05yYhOHxoI2b4gGyI96kEcmadMisZodiOaF SuP7MFfxMYn4PoBNVH+BLwuRonWFo7BrdHPmVSD5SP0nLqxjkEnM3LxpCcIKVKx60FHy Se2yx91t+QvgZg/2pX54p75aA8McbkUR/FvYjIT1UGtdbnDbzMbBPZpBsMNrEGbNi1GU KkG4Np6MH5DSX1QTng+RtnwvTQOn0KLrIeWBTGHsQS4iyDRP5pQO/Khw5HgCieFHfDRD 4Z4w== X-Gm-Message-State: APjAAAXkLd5p8sm1Nck38bf3YFp9zAHvO6Z7HOqb3WVIqgq20BkCnmHL Czwqvay723qTQYyn9SZm1hfeDgqP X-Google-Smtp-Source: APXvYqxI8mL2kPmjK2pEVhEL/dy8DqjI6OaSSQflavwt0BY2JUXlgBNy2kIYm/FyVKzp4LyWBBitMQ== X-Received: by 2002:ac8:f77:: with SMTP id l52mr3337782qtk.310.1578488260302; Wed, 08 Jan 2020 04:57:40 -0800 (PST) Received: from frodo.corp.eldorado.org.br ([200.168.210.66]) by smtp.gmail.com with ESMTPSA id z6sm1283615qkz.101.2020.01.08.04.57.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Jan 2020 04:57:39 -0800 (PST) From: Andre Silva To: qemu-devel@nongnu.org Subject: [PATCH] virtio: Prevent double swap due to target pre 1.0 VirtIO Date: Wed, 8 Jan 2020 09:56:57 -0300 Message-Id: <20200108125658.208480-1-afscoelho@gmail.com> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::841 X-Mailman-Approved-At: Wed, 08 Jan 2020 08:43:53 -0500 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: mst@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Remove the bswap function calls after reading and before writing memory bytes in virtio_pci_config_read and virtio_pci_config_write because they are reverting back an already swapped bytes. Consider the table below in the context of virtio_pci_config_read 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 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)' means that Qemu will use a swapped value. If we remove the extra swap made in virtio_pci_config_read we will 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(void *opaque, hwaddr addr, break; case 2: val = virtio_config_readw(vdev, addr); - if (virtio_is_big_endian(vdev)) { - val = bswap16(val); - } break; case 4: val = virtio_config_readl(vdev, addr); - if (virtio_is_big_endian(vdev)) { - val = 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 = bswap16(val); - } virtio_config_writew(vdev, addr, val); break; case 4: - if (virtio_is_big_endian(vdev)) { - val = bswap32(val); - } virtio_config_writel(vdev, addr, val); break; } -- 2.24.1