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=-4.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 DB7B2C433E2 for ; Mon, 7 Sep 2020 09:47:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A128A2078E for ; Mon, 7 Sep 2020 09:47:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599472030; bh=cFHskjvmHO3vzxD+eGBoRNZ+sFpiHGFme6jLOuWP8Uc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=KfE7oDZoKWtcURdwnxwUSQLumJLQnrZD+dGJI/pc/Q6Jx6c1ZU8LNSWYrOB9o0BJt I2JmFCPLskODfV69aig8wNIOl6Wnh5OwvJuzfmtKO6O26IHPmQi61XwBrZBMOWfI/y 3EbmvT2xowr+OommMeGuduWmQ9lGES3tn6+Ps4qI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728395AbgIGJrF (ORCPT ); Mon, 7 Sep 2020 05:47:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:44148 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726301AbgIGJrE (ORCPT ); Mon, 7 Sep 2020 05:47:04 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 49EFA2078E; Mon, 7 Sep 2020 09:47:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599472023; bh=cFHskjvmHO3vzxD+eGBoRNZ+sFpiHGFme6jLOuWP8Uc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=19AbdD+EC1bO4XviCsVbOEsgKBlvuTcIcRwYpDXdAbiyDIC2ngljNeSByIj6g2WwR pwHlJAa2zca7ViqS+HXJHlbRqiyn/WpxFytm5SMsvxtaqOBqDi0a5jaudF1eVdGURu jTZbUs3gK3gLc/gZXJVqSV1JOAEE6FHqZ7nCuP54= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1kFDjp-009iuT-BE; Mon, 07 Sep 2020 10:47:01 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 07 Sep 2020 10:47:01 +0100 From: Marc Zyngier To: Jianyong Wu Cc: netdev@vger.kernel.org, yangbo.lu@nxp.com, john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com, sean.j.christopherson@intel.com, richardcochran@gmail.com, Mark Rutland , will@kernel.org, Suzuki Poulose , Steven Price , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Steve Capper , Justin He , nd Subject: Re: [PATCH v14 08/10] ptp: arm64: Enable ptp_kvm for arm64 In-Reply-To: References: <20200904092744.167655-1-jianyong.wu@arm.com> <20200904092744.167655-9-jianyong.wu@arm.com> <874kocmqqx.wl-maz@kernel.org> <366387fa507f9c5d5044549cea958ce1@kernel.org> User-Agent: Roundcube Webmail/1.4.8 Message-ID: <67f3381467d02c8d3f25682cd99898e9@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: Jianyong.Wu@arm.com, netdev@vger.kernel.org, yangbo.lu@nxp.com, john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com, sean.j.christopherson@intel.com, richardcochran@gmail.com, Mark.Rutland@arm.com, will@kernel.org, Suzuki.Poulose@arm.com, Steven.Price@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Steve.Capper@arm.com, Justin.He@arm.com, nd@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2020-09-07 10:28, Jianyong Wu wrote: >> -----Original Message----- >> From: Marc Zyngier >> Sent: Monday, September 7, 2020 4:55 PM >> To: Jianyong Wu [...] >> >> arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_FEATUR >> >> ES_FUNC_ID, >> >> > + &hvc_res); >> >> > + if (!(hvc_res.a0 | BIT(ARM_SMCCC_KVM_FUNC_KVM_PTP))) >> >> > + return -EOPNOTSUPP; >> >> > + >> >> > + return 0; >> >> >> >> What happens if the >> >> ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID function isn't >> implemented >> >> (on an old kernel or a non-KVM hypervisor)? The expected behaviour is >> >> that a0 will contain SMCCC_RET_NOT_SUPPORTED, which is -1. >> >> The result is that this function always returns "supported". Not an >> >> acceptable behaviour. >> >> >> > Oh! it's really a stupid mistake, should be "&" not "|". >> >> But even then. (-1 & whatever) is always true. > > Yeah, what about checking if a0 is non-negative first? Like: > if (hvc_res.a0 < 0 || !(hvc_res.a0 & BIT(ARM_SMCCC_KVM_FUNC_KVM_PTP))) > return -EOPNOTSUPP; I don't get it. You already carry a patch from Will that gives you a way to check for a service (kvm_arm_hyp_service_available()). Why do you need to reinvent the wheel? M. -- Jazz is not dead. It just smells funny...