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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 5CA25C31E5B for ; Tue, 18 Jun 2019 01:26:43 +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 346502082C for ; Tue, 18 Jun 2019 01:26:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 346502082C 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 ([::1]:52878 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hd2tV-0002V9-SY for qemu-devel@archiver.kernel.org; Mon, 17 Jun 2019 21:26:41 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39259) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hd2sN-00025x-9y for qemu-devel@nongnu.org; Mon, 17 Jun 2019 21:25:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hd2sE-0008Vi-Nx for qemu-devel@nongnu.org; Mon, 17 Jun 2019 21:25:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52268) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hd2sE-0008DM-4S for qemu-devel@nongnu.org; Mon, 17 Jun 2019 21:25:22 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2CFDC30917A6; Tue, 18 Jun 2019 01:25:03 +0000 (UTC) Received: from ovpn-116-47.sin2.redhat.com (ovpn-116-47.sin2.redhat.com [10.67.116.47]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3C2108095E; Tue, 18 Jun 2019 01:24:58 +0000 (UTC) Message-ID: <1560821097.5084.179.camel@redhat.com> From: Vadim Rozenfeld To: Eduardo Habkost , Roman Kagan , Vitaly Kuznetsov , qemu-devel@nongnu.org, Paolo Bonzini , Richard Henderson Date: Tue, 18 Jun 2019 11:24:57 +1000 In-Reply-To: <20190617174917.GE19178@habkost.net> References: <20190615200505.31348-1-ehabkost@redhat.com> <20190617134856.GF32624@rkaganb.sw.ru> <20190617142301.GA19178@habkost.net> <20190617173210.GG32624@rkaganb.sw.ru> <20190617174917.GE19178@habkost.net> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Tue, 18 Jun 2019 01:25:03 +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] [PATCH] i386: Fix signedness of hyperv_spinlock_attempts 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 2019-06-17 at 14:49 -0300, Eduardo Habkost wrote: > On Mon, Jun 17, 2019 at 05:32:13PM +0000, Roman Kagan wrote: > > On Mon, Jun 17, 2019 at 11:23:01AM -0300, Eduardo Habkost wrote: > > > On Mon, Jun 17, 2019 at 01:48:59PM +0000, Roman Kagan wrote: > > > > On Sat, Jun 15, 2019 at 05:05:05PM -0300, Eduardo Habkost > > > > wrote: > > > > > The current default value for hv-spinlocks is 0xFFFFFFFF > > > > > (meaning > > > > > "never retry"). However, the value is stored as a signed > > > > > integer, making the getter of the hv-spinlocks QOM property > > > > > return -1 instead of 0xFFFFFFFF. > > > > > > > > > > Fix this by changing the type of > > > > > X86CPU::hyperv_spinlock_attempts > > > > > to uint32_t. This has no visible effect to guest operating > > > > > systems, affecting just the behavior of the QOM getter. > > > > > > > > > > Signed-off-by: Eduardo Habkost > > > > > --- > > > > > target/i386/cpu.h | 2 +- > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > Reviewed-by: Roman Kagan > > > > > > > > That said, it's tempting to just nuke qdev_prop_spinlocks and > > > > make > > > > hv-spinlocks a regular DEFINE_PROP_UINT32... > > > > > > Agreed. The only difference is that we would validate the > > > property at realize time instead of object_property_set(). > > > > Right. But currently it's validated to be no less than 0xfff and > > no > > bigger than 0xffffffff. The latter check would become unnecessary, > > and > > I'm unable to find any reason to do the former (neither spec > > references > > nor the log messages of the commits that introduced it). > > The 0xFFF lower limit was originally introduced by commit > 28f52cc04d34 ("hyper-v: introduce Hyper-V support infrastructure"). > > Vadim, do you know where the 0xFFF limit comes from? I simply took this value from Windows Server 2008 R2 that I used as a reference while working on Hyper-V support for KVM. I also remember some paper (probably published by AMD ???) mentioned that 0x2fff seemed to have the best balance for PLE logic. Best, Vadim.