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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 8CA6CC19759 for ; Thu, 1 Aug 2019 11:08:13 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 5B73A2087E for ; Thu, 1 Aug 2019 11:08:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="CxB1sSEq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B73A2087E Authentication-Results: mail.kernel.org; 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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1ht8wI-0002UC-Mf; Thu, 01 Aug 2019 11:08:06 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1ht8wF-0002TU-Ea for linux-arm-kernel@lists.infradead.org; Thu, 01 Aug 2019 11:08:04 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EA8EB1570; Thu, 1 Aug 2019 04:08:00 -0700 (PDT) Received: from [10.1.197.61] (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 86B9D3F575; Thu, 1 Aug 2019 04:07:59 -0700 (PDT) Subject: Re: [PATCH] arm64: Relax ICC_PMR_EL1 accesses when ICC_CTLR_EL1.PMHE is clear To: Julien Thierry References: <1564496445-53486-1-git-send-email-julien.thierry.kdev@gmail.com> <20190801104119.quzlr5artm4s2sbc@willie-the-truck> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; 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Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190801_040803_582074_50D28A3D X-CRM114-Status: GOOD ( 17.78 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marc Zyngier , Will Deacon , Suzuki K Poulose , Catalin Marinas , James Morse , huawei.libin@huawei.com, guohanjun@huawei.com, liwei391@huawei.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 01/08/2019 11:56, Julien Thierry wrote: > On Thu, 1 Aug 2019 at 11:51, Marc Zyngier wrote: >> >> On 01/08/2019 11:41, Will Deacon wrote: >>> On Tue, Jul 30, 2019 at 03:20:45PM +0100, Julien Thierry wrote: >>>> From: Marc Zyngier >>>> >>>> The GICv3 architecture specification is incredibly misleading when it >>>> comes to PMR and the requirement for a DSB. It turns out that this DSB >>>> is only required if the CPU interface sends an Upstream Control >>>> message to the redistributor in order to update the RD's view of PMR. >>>> >>>> This message is only sent when ICC_CTLR_EL1.PMHE is set, which isn't >>>> the case in Linux. It can still be set from EL3, so some special care >>>> is required. But the upshot is that in the (hopefuly large) majority >>>> of the cases, we can drop the DSB altogether. >>>> >>>> This requires yet another capability and some more runtime patching. >>> >>> Hmm, does this actually require explicit runtime patching, or can we make >>> things a bit simpler with a static key? >> >> The hunk in entry.S is the blocker, AFAICS. Do we have a way to express >> static keys in asm? >> > > Not that I'm aware of. I could leave the alternative in entry.S and > use a static_key for the pmr_sync() macro. I'm not sure that helps. It means we end-up with two mechanisms to keep in sync instead of a single one. > Does it change much over all? I don't see the static key simplifying > things too much, but I don't mind using that instead. The complexity is the same. The added benefit is that we can control it from the GIC code rather than the architecture code. But that's assuming we can do it all using a static key... Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel