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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 6D08FC4740C for ; Mon, 9 Sep 2019 15:48:15 +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 43BF12082C for ; Mon, 9 Sep 2019 15:48:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 43BF12082C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=sipsolutions.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58280 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7Ltm-0006Yj-Cz for qemu-devel@archiver.kernel.org; Mon, 09 Sep 2019 11:48:14 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57267) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7Lsy-0005rM-9h for qemu-devel@nongnu.org; Mon, 09 Sep 2019 11:47:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i7Lsx-0001UX-7n for qemu-devel@nongnu.org; Mon, 09 Sep 2019 11:47:24 -0400 Received: from s3.sipsolutions.net ([2a01:4f8:191:4433::2]:49612 helo=sipsolutions.net) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i7Lsx-0001Sv-1J for qemu-devel@nongnu.org; Mon, 09 Sep 2019 11:47:23 -0400 Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1i7Lsu-0000I0-RY; Mon, 09 Sep 2019 17:47:20 +0200 Message-ID: From: Johannes Berg To: "Michael S. Tsirkin" Date: Mon, 09 Sep 2019 17:47:19 +0200 In-Reply-To: <20190909114358-mutt-send-email-mst@kernel.org> References: <20190908091207-mutt-send-email-mst@kernel.org> <8a9cf8a1726afce7fed8992a4f19fc808004ef88.camel@sipsolutions.net> <20190909083902-mutt-send-email-mst@kernel.org> <89f25546ffa71c799c533e50658a3a58e066f436.camel@sipsolutions.net> <20190909094609-mutt-send-email-mst@kernel.org> <20190909105057-mutt-send-email-mst@kernel.org> <49378faefb98abafb64ff105a7941c47395426e7.camel@sipsolutions.net> <20190909114358-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a01:4f8:191:4433::2 Subject: Re: [Qemu-devel] [RFC] libvhost-user: implement VHOST_USER_PROTOCOL_F_KICK_CALL_MSGS 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-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 2019-09-09 at 11:45 -0400, Michael S. Tsirkin wrote: > On Mon, Sep 09, 2019 at 05:34:13PM +0200, Johannes Berg wrote: > > On Mon, 2019-09-09 at 17:26 +0200, Johannes Berg wrote: > > > Maybe instead we should just add a "VHOST_USER_REPLY_ERROR" bit (e.g. > > > bit 4 after NEED_REPLY). Qemu in vhost_user_read_header() validates that > > > it received REPLY_MASK | VERSION, so it would reject the message at that > > > point. > > > > > > Another possibility would be to define the highest bit of the 'request' > > > field to indicate an error, so for GET_FEATURES we'd return the value > > > 0x80000000 | GET_FEATURES. > > > > However, one way or another, that basically leaves us with three > > different ways of indicating an error: > > > > 1) already defined errors in existing messages - we can't change them > > since those are handled at runtime now, e.g. VHOST_USER_POSTCOPY_END > > returns a u64 value with an error status, and current code cannot > > deal with an error flag in the 'request' or 'flags' field > > 2) F_REPLY_ACK errors to messages that do not specify a response at all > > 3) this new way of indicating an error back from messages that specify > > a response, but the response has no inherent way of returning an > > error > > > > To me that really feels a bit too complex from the spec POV. But I don't > > see a way to generalize this without another extension, and again the > > device cannot choose which extensions it supports since the master > > chooses them and just sets them. > > > > Perhaps I really should just stick a "g_assert()" into the code at that > > point, > > There's the old way: close the socket. > This will make reads fail gracefully. > If we don't want complexity right now, I'd go with that. D'oh, good point. OK, I'll do that. Though it's almost equivalent in libvhost-user to just asserting, since it's mostly set up to just handle a single connection and then quit. Alright, thanks. Like I said, I'll send some more patches all around once I get it working, right now I'm crashing in some weird ways that I need to debug :) johannes