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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B17EFC433F5 for ; Wed, 2 Mar 2022 17:12:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=OQMQJTDoOO28MJgQToO/b5L9NHpSk7rvDFGKfqyoNxA=; b=oKzfG1WN09pXUp /NQvmSTVLxgkFwzXYKwVQbR17xJ5YzCjXxfItoqIvsPAraCdg6nmrTNT96esQJgtA8A6sS2rBc3mj Bqj2HIvzlpF2nDd0UWh2pPMAgo87j/GuV7y0GA0J969JTGOlKz06tn6zDeWcn+371apyTsc3KENJ5 irhHk+B1/BZbzotuelcRNSl/Xu5iczq5o9hk7DCsimS6pgSrtpZMPsBJQzaMGHuD716h6w7UeOD6X F3zcfN7MZtF+Tk9IIvSt1eU9iW4eMdBjk7dG+GSdH9h07FEhu35IKehUWBIB/5OFOh00raqEsLQLZ ROI4J9PxVHyGdyJBGrQg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nPSVm-003U2m-5v; Wed, 02 Mar 2022 17:11:38 +0000 Received: from ams.source.kernel.org ([2604:1380:4601:e00::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nPSVi-003U1p-B9 for linux-arm-kernel@lists.infradead.org; Wed, 02 Mar 2022 17:11:35 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id F1BEAB82109; Wed, 2 Mar 2022 17:11:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE8DEC340ED; Wed, 2 Mar 2022 17:11:28 +0000 (UTC) Date: Wed, 2 Mar 2022 17:11:25 +0000 From: Catalin Marinas To: Mark Brown Cc: Will Deacon , Marc Zyngier , Shuah Khan , Shuah Khan , Alan Hayward , Luis Machado , Salil Akerkar , Basant Kumar Dwivedi , Szabolcs Nagy , James Morse , Alexandru Elisei , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org, kvmarm@lists.cs.columbia.edu Subject: Re: [PATCH v12 22/40] arm64/sme: Implement ptrace support for streaming mode SVE registers Message-ID: References: <20220225165923.1474372-1-broonie@kernel.org> <20220225165923.1474372-23-broonie@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220225165923.1474372-23-broonie@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220302_091134_547457_7E982DF0 X-CRM114-Status: GOOD ( 17.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Feb 25, 2022 at 04:59:05PM +0000, Mark Brown wrote: > The streaming mode SVE registers are represented using the same data > structures as for SVE but since the vector lengths supported and in use > may not be the same as SVE we represent them with a new type NT_ARM_SSVE. > Unfortunately we only have a single 16 bit reserved field available in > the header so there is no space to fit the current and maximum vector > length for both standard and streaming SVE mode without redefining the > structure in a way the creates a complicatd and fragile ABI. Since FFR > is not present in streaming mode it is read and written as zero. > > Setting NT_ARM_SSVE registers will put the task into streaming mode, > similarly setting NT_ARM_SVE registers will exit it. Reads that do not > correspond to the current mode of the task will return the header with > no register data. For compatibility reasons on write setting no flag for > the register type will be interpreted as setting SVE registers, though > users can provide no register data as an alternative mechanism for doing > so. > > Signed-off-by: Mark Brown Reviewed-by: Catalin Marinas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel