From nobody Tue May 21 17:03:33 2024 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=gmail.com ARC-Seal: i=1; a=rsa-sha256; t=1578500433; cv=none; d=zohomail.com; s=zohoarc; b=hdzArAZAfDcb86mGRzOUYujj09I2SXsHitQbsWEkEkOkSBmhgmzEIDvlGAc/HinoLnSLRAaC6/rFBrvwxgPv7LxHfmbvK5Tnd7VvFEk8f1iDXqigrnrVtaa4awxNq/6JvAoP4XXMd5cFIChjukk9Ev30eRrGLLWyqGQfbfF3whc= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1578500433; h=Content-Transfer-Encoding:Cc:Date:From:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Sender:Subject:To; bh=BJ2O4PQRw1ys8DhPlVU2A3mHoRVTkwiCzLu+4EEMMFE=; b=CELI0nRfiHIMTUDMKVn2JRdL+CA1MBxZthv3S0AOncsd2YdrIC2JcKgkbVnyFarKcb2nAdT+n3Tmw+N2Hj8HU+FzHmUvaB/Pxlyp6ODPgUnMyXorCQxmuAYBZI+AldKE6HUfPc6ukASKW2EsIdo5BMkkpdtupXtRtYQB2wY6jns= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1578500433495978.9453301367505; Wed, 8 Jan 2020 08:20:33 -0800 (PST) Received: from localhost ([::1]:46280 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ipE4O-0003Fb-CE for importer@patchew.org; Wed, 08 Jan 2020 11:20:32 -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) 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) 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) 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: quoted-printable 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @gmail.com) Content-Type: text/plain; charset="utf-8" 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, h= waddr 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, hwad= dr 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; } --=20 2.24.1