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 076DAC282DD for ; Wed, 8 Jan 2020 16:20:31 +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 C405120678 for ; Wed, 8 Jan 2020 16:20:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="tJ+1NK+O" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C405120678 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]:46280 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipE4L-0003Fb-RJ for qemu-devel@archiver.kernel.org; Wed, 08 Jan 2020 11:20:29 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:44577) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipE0i-0007xn-Vv for qemu-devel@nongnu.org; Wed, 08 Jan 2020 11:16:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ipE0a-0004kq-H0 for qemu-devel@nongnu.org; Wed, 08 Jan 2020 11:16:43 -0500 Received: from mail-qk1-x743.google.com ([2607:f8b0:4864:20::743]:34864) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ipE0W-0004j3-N9 for qemu-devel@nongnu.org; Wed, 08 Jan 2020 11:16:36 -0500 Received: by mail-qk1-x743.google.com with SMTP id z76so3150544qka.2 for ; Wed, 08 Jan 2020 08:16:32 -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=tJ+1NK+OC5v7dBp0vRQzFhCsJlYYvbNLFixpC1XWBxAwTjexFIsNf5WdqZk58O56ZL ggliuwXgwhevjdCr8++rzegHixitU6lElOJyX0YegvVmDLpGKnXACnH0O3lW+cL+BB6F EJ/U+cTFxinrVvoEQl6PcjmqJ9fCVbKiGu/oFkNUTqX8iUs9lDrL3RZq4RXfBNLc1Y1M SWFKrnCcd4oIlXEitvjwcjrAv5njNAyjhTruzL3w156HLN8DySJUn/pDQh4A1wW5yggs T384v6+myea8Lb38FrjH9qwC9qGv+oR30ESOVwUUUQsxK+dbniaVRrpU27ox99gaQ2ZK teQQ== 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=Y/kiy/iYTpkLd9rabEHlZWmWG/udCJU8oBymddmrwgSMY6SiU0WoosfoOI5muDc3LO AAmb1243X9hJ9ha90qN0KsIOHHAFFpdoxpcJ8cn2q1Ys+ska92uTCd+1meXd/DYn7Hy5 a7lOArrvbnzmiP5BgMMpsK1LVNyZSU3cpfZEeM640eI7wE+8rYnIKHhgx47Jqq76I/rQ C5IKu11z05VIQgLydc/fOBy10H9mj3XAY70j+hDSMi478PzsdiA1QVn8JJENK7c8LzH2 mFgzEr/iS1yqUy3UO9EW6hNoyXP2ESU9ex7Np14FYOoXUPCeF3Bhs71X1y5ZFt1NHf6c tS9w== X-Gm-Message-State: APjAAAW2tW88zN9qQL5v2yJynV2u8ApiWS+ulDyZRvCz+K1b8v+xZqxE HIX3ocdRVF9HHDsFvwmT9Pm1Z7v3 X-Google-Smtp-Source: APXvYqzVv+fvPqtOarR35xAn7Isza8NAP+NZElfa8j5nllAz89hwN33V+8CuHF4Gz1zmRFveavuWRA== X-Received: by 2002:a05:620a:947:: with SMTP id w7mr5052259qkw.432.1578500191483; Wed, 08 Jan 2020 08:16:31 -0800 (PST) Received: from frodo.corp.eldorado.org.br ([200.168.210.66]) by smtp.gmail.com with ESMTPSA id u5sm1578200qkj.127.2020.01.08.08.16.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Jan 2020 08:16:30 -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 13:16:18 -0300 Message-Id: <20200108161618.221116-1-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::743 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