From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:48588) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH58Q-0004k3-QT for qemu-devel@nongnu.org; Thu, 18 Apr 2019 07:23:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hH58P-0004hP-UK for qemu-devel@nongnu.org; Thu, 18 Apr 2019 07:23:18 -0400 Date: Thu, 18 Apr 2019 13:23:08 +0200 From: Kevin Wolf Message-ID: <20190418112308.GD5242@linux.fritz.box> References: <20190417115343.30527-1-pbonzini@redhat.com> <20190418104737.GC5242@linux.fritz.box> <87b281df-e0a0-6537-0e1a-4c6af28ffc01@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87b281df-e0a0-6537-0e1a-4c6af28ffc01@redhat.com> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH] scsi-generic: prevent guest from exceeding SG_IO limits List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Stefan Hajnoczi , Stefan Hajnoczi , qemu-devel , qemu block , qemu-stable Am 18.04.2019 um 13:01 hat Paolo Bonzini geschrieben: > On 18/04/19 12:47, Kevin Wolf wrote: > >> This is acually only an issue with kernels prior to 4.5, so it should be > >> fixed downstream instead. > > > > I don't think that upstream QEMU has kernels > 4.5 as an official > > requirement, though? We try to be compatible with quite old libs, so we > > should stay compatible with old kernels, too. > > It is a pretty rare case, where the host must support very large > scatter/gather lists (>=1024 elements) and there is a workaround by > setting max_sectors_kb to 4096 in the host. It also makes performance > worse. Fair enough. I didn't consider that it has a performance impact even on newer kernels that don't need the patch. Kevin 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=-2.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 911BBC10F0E for ; Thu, 18 Apr 2019 11:24:38 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5DDA5214DA for ; Thu, 18 Apr 2019 11:24:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5DDA5214DA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:39661 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH59h-0005fP-Kk for qemu-devel@archiver.kernel.org; Thu, 18 Apr 2019 07:24:37 -0400 Received: from eggs.gnu.org ([209.51.188.92]:48588) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH58Q-0004k3-QT for qemu-devel@nongnu.org; Thu, 18 Apr 2019 07:23:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hH58P-0004hP-UK for qemu-devel@nongnu.org; Thu, 18 Apr 2019 07:23:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57212) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hH58N-0004fX-S5; Thu, 18 Apr 2019 07:23:15 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 23D323086227; Thu, 18 Apr 2019 11:23:15 +0000 (UTC) Received: from linux.fritz.box (ovpn-116-132.ams2.redhat.com [10.36.116.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C3C0460BEC; Thu, 18 Apr 2019 11:23:10 +0000 (UTC) Date: Thu, 18 Apr 2019 13:23:08 +0200 From: Kevin Wolf To: Paolo Bonzini Message-ID: <20190418112308.GD5242@linux.fritz.box> References: <20190417115343.30527-1-pbonzini@redhat.com> <20190418104737.GC5242@linux.fritz.box> <87b281df-e0a0-6537-0e1a-4c6af28ffc01@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <87b281df-e0a0-6537-0e1a-4c6af28ffc01@redhat.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Thu, 18 Apr 2019 11:23:15 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [Qemu-block] [PATCH] scsi-generic: prevent guest from exceeding SG_IO limits 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: Stefan Hajnoczi , qemu block , qemu-devel , Stefan Hajnoczi , qemu-stable Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190418112308.BPpn-d4PPtNjlwldXI62thojdqao4FO9YoLhDvRGbWw@z> Am 18.04.2019 um 13:01 hat Paolo Bonzini geschrieben: > On 18/04/19 12:47, Kevin Wolf wrote: > >> This is acually only an issue with kernels prior to 4.5, so it should be > >> fixed downstream instead. > > > > I don't think that upstream QEMU has kernels > 4.5 as an official > > requirement, though? We try to be compatible with quite old libs, so we > > should stay compatible with old kernels, too. > > It is a pretty rare case, where the host must support very large > scatter/gather lists (>=1024 elements) and there is a workaround by > setting max_sectors_kb to 4096 in the host. It also makes performance > worse. Fair enough. I didn't consider that it has a performance impact even on newer kernels that don't need the patch. Kevin