From nobody Mon Feb 9 16:19:15 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1508789795665329.94485452167896; Mon, 23 Oct 2017 13:16:35 -0700 (PDT) Received: from localhost ([::1]:40400 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e6j96-00047I-N0 for importer@patchew.org; Mon, 23 Oct 2017 16:16:24 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46131) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e6j4F-00009g-M9 for qemu-devel@nongnu.org; Mon, 23 Oct 2017 16:11:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e6j4E-0002TZ-G4 for qemu-devel@nongnu.org; Mon, 23 Oct 2017 16:11:23 -0400 Received: from mail-pf0-x242.google.com ([2607:f8b0:400e:c00::242]:51657) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1e6j4B-0002Rb-LB; Mon, 23 Oct 2017 16:11:19 -0400 Received: by mail-pf0-x242.google.com with SMTP id n14so17898264pfh.8; Mon, 23 Oct 2017 13:11:19 -0700 (PDT) Received: from squirtle.westlake.spaceflightindustries.com ([173.226.206.194]) by smtp.gmail.com with ESMTPSA id j1sm15181623pfj.108.2017.10.23.13.11.17 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 23 Oct 2017 13:11:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=+YqRSUlO8UVt4KhrEMRENRxa2VJKL09ZOzda1SuGMZY=; b=SvbAt/k0Xu4k36rfPaApvoaBgdPkDLY3b77kTPj7mSj8iMsiUqwVNwL8o7U0dCet7J EAS+XPY36z8ftroZjuIAlEm+kflCIrltHB3Ho4qWzzPYsM9avC+9o05gOBHJIGJ1Jcxb CpXxUi8HkN2WHFogsfjMgY+AzDal3o8c8ziI2yKtDR++w81Zd9yti1SINSJKyZSpLgNu CsSHbxiIdkFXGg/38mNM70+52IMKelq9rJ4FsXEzT78xtQ0K/5QV+m9M65laLFWSzaWl c17F7nO+I32djCCkIyWV6L7P3oAOe1hFpzGGDZcegDDlcY0It0OkJVxrG9+g6twPDHqH io8A== 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=+YqRSUlO8UVt4KhrEMRENRxa2VJKL09ZOzda1SuGMZY=; b=mfarxPI6R/qDqmVZDvIuLPbYGAUEQOI53IAZyeVQJbnpK3xzDrrtmAWpw4y2NNt8xb A8vE2f1ZMbEh8xNAcYYKTgn9dDg2EgPYnXiuyD5iM2bCF1tTFaOayRYHKQdeNRFxj+xl JxDix71cbxCgV6se4wbX2zOHBhtQwRnE2H2DCEMmumnCckF+jAqjobm8EXgEwpSzPUaX aCUnewtt325SbtWQNCepKAXkORiwBN0az0muDMUszEO1lx2B6FskfSSaRgShGeN6zR08 +7JfTeoB/qKBtppLEE9nXD/Qv74HD2qyTcSbM2k/tbUc3Sgx05vY7yvAhkuL+987wN+o tmvA== X-Gm-Message-State: AMCzsaX1iIoPod6uOdRUIlWLjHtO2RKja/dm6pagQkhHyMVnv74eqq2t RYp6dFxiz1ShnS88SkqiPwAIsNaH X-Google-Smtp-Source: ABhQp+RzzKVPnZIRB8XFi6IY255N1cd7EAalNnR0zVX05t73YUaE1iLw14CKd0Xh62aA4r2KDAPBHw== X-Received: by 10.99.114.24 with SMTP id n24mr12508572pgc.253.1508789478379; Mon, 23 Oct 2017 13:11:18 -0700 (PDT) From: Andrey Smirnov To: qemu-arm@nongnu.org Date: Mon, 23 Oct 2017 13:10:31 -0700 Message-Id: <20171023201055.21973-4-andrew.smirnov@gmail.com> X-Mailer: git-send-email 2.13.5 In-Reply-To: <20171023201055.21973-1-andrew.smirnov@gmail.com> References: <20171023201055.21973-1-andrew.smirnov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:400e:c00::242 Subject: [Qemu-devel] [PATCH v2 03/27] imx_fec: Change queue flushing heuristics X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Andrey Smirnov , Jason Wang , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, yurovsky@gmail.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDKM_2 RSF_0 Z_629925259 SPT_0 In current implementation, packet queue flushing logic seem to suffer from a deadlock like scenario if a packet is received by the interface before before Rx ring is initialized by Guest's driver. Consider the following sequence of events: 1. A QEMU instance is started against a TAP device on Linux host, running Linux guest, e. g., something to the effect of: qemu-system-arm \ -net nic,model=3Dimx.fec,netdev=3Dlan0 \ netdev tap,id=3Dlan0,ifname=3Dtap0,script=3Dno,downscript=3Dno \ ... rest of the arguments ... 2. Once QEMU starts, but before guest reaches the point where FEC deriver is done initializing the HW, Guest, via TAP interface, receives a number of multicast MDNS packets from Host (not necessarily true for every OS, but it happens at least on Fedora 25) 3. Recieving a packet in such a state results in imx_eth_can_receive() returning '0', which in turn causes tap_send() to disable corresponding event (tap.c:203) 4. Once Guest's driver reaches the point where it is ready to recieve packets it prepares Rx ring descriptors and writes ENET_RDAR_RDAR to ENET_RDAR register to indicate to HW that more descriptors are ready. And at this points emulation layer does this: s->regs[index] =3D ENET_RDAR_RDAR; imx_eth_enable_rx(s); which, combined with: if (!s->regs[ENET_RDAR]) { qemu_flush_queued_packets(qemu_get_queue(s->nic)); } results in Rx queue never being flushed and corresponding I/O event beign disabled. To prevent the problem, change the code to always flush packet queue when ENET_RDAR transitions 0 -> ENET_RDAR_RDAR. Cc: Peter Maydell Cc: Jason Wang Cc: Philippe Mathieu-Daud=C3=A9 Cc: qemu-devel@nongnu.org Cc: qemu-arm@nongnu.org Cc: yurovsky@gmail.com Signed-off-by: Andrey Smirnov --- hw/net/imx_fec.c | 12 ++++++------ include/hw/net/imx_fec.h | 1 + 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c index 8b2e4b8ffe..eb034ffd0c 100644 --- a/hw/net/imx_fec.c +++ b/hw/net/imx_fec.c @@ -533,7 +533,7 @@ static void imx_eth_do_tx(IMXFECState *s) } } =20 -static void imx_eth_enable_rx(IMXFECState *s) +static void imx_eth_enable_rx(IMXFECState *s, bool flush) { IMXFECBufDesc bd; bool rx_ring_full; @@ -544,7 +544,7 @@ static void imx_eth_enable_rx(IMXFECState *s) =20 if (rx_ring_full) { FEC_PRINTF("RX buffer full\n"); - } else if (!s->regs[ENET_RDAR]) { + } else if (flush) { qemu_flush_queued_packets(qemu_get_queue(s->nic)); } =20 @@ -807,7 +807,7 @@ static void imx_eth_write(void *opaque, hwaddr offset, = uint64_t value, if (s->regs[ENET_ECR] & ENET_ECR_ETHEREN) { if (!s->regs[index]) { s->regs[index] =3D ENET_RDAR_RDAR; - imx_eth_enable_rx(s); + imx_eth_enable_rx(s, true); } } else { s->regs[index] =3D 0; @@ -930,7 +930,7 @@ static int imx_eth_can_receive(NetClientState *nc) =20 FEC_PRINTF("\n"); =20 - return s->regs[ENET_RDAR] ? 1 : 0; + return !!s->regs[ENET_RDAR]; } =20 static ssize_t imx_fec_receive(NetClientState *nc, const uint8_t *buf, @@ -1020,7 +1020,7 @@ static ssize_t imx_fec_receive(NetClientState *nc, co= nst uint8_t *buf, } } s->rx_descriptor =3D addr; - imx_eth_enable_rx(s); + imx_eth_enable_rx(s, false); imx_eth_update(s); return len; } @@ -1116,7 +1116,7 @@ static ssize_t imx_enet_receive(NetClientState *nc, c= onst uint8_t *buf, } } s->rx_descriptor =3D addr; - imx_eth_enable_rx(s); + imx_eth_enable_rx(s, false); imx_eth_update(s); return len; } diff --git a/include/hw/net/imx_fec.h b/include/hw/net/imx_fec.h index 62ad473b05..4bc8f03ec2 100644 --- a/include/hw/net/imx_fec.h +++ b/include/hw/net/imx_fec.h @@ -252,6 +252,7 @@ typedef struct IMXFECState { uint32_t phy_int_mask; =20 bool is_fec; + bool needs_flush; } IMXFECState; =20 #endif --=20 2.13.5