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=-9.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,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 28204C47080 for ; Tue, 1 Jun 2021 14:00:02 +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 D3EFB61376 for ; Tue, 1 Jun 2021 14:00:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D3EFB61376 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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:MIME-Version:References:In-Reply-To: Subject:Cc:To:From:Message-ID:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=NyFjPJ96U9AjJJvGa4tLerQ+I0SU9V/IKSu7bgwlKQM=; b=HFnSDlb1aCfnGK v5c/YFbqBUd5lkEf0MEXYeddbqQXqKSrw9WlqWpFsXqyv5fWrYTaCKfhjKT6q0+h9kJ6eM2JKJROz ysgNA7a/MCZQhFVVN7vyY+2xwRHxEXHsMisAyTsuGXZhovju+SQuuD50Zypi0hqdKrK1IU0eQFv7d qMNCQfaeCsBMNct5qbWuTnPaJ+mdPD8aZcQPp/o1tJt1ZywZN8Tp9QjDSPiaSAKcPegJ+3gC+naL5 HdTFa57Z9uHKsnUkuAvoAzkKPx1cnlw+SI/rZ6aJFXTgS0utr8qwuNMhUCWQrqgjKOP3MVKpfpd/n Vb4V9pc6Oq6NWjS820ew==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lo4uj-00GugG-CA; Tue, 01 Jun 2021 13:58:37 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lo4ue-00GueQ-Hf for linux-arm-kernel@lists.infradead.org; Tue, 01 Jun 2021 13:58:34 +0000 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 915CE600CD; Tue, 1 Jun 2021 13:58:31 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lo4ub-004pVR-MV; Tue, 01 Jun 2021 14:58:29 +0100 Date: Tue, 01 Jun 2021 14:58:29 +0100 Message-ID: <87mts91ybe.wl-maz@kernel.org> From: Marc Zyngier To: Mark Brown Cc: Catalin Marinas , Will Deacon , Lorenzo Pieralisi , Sudeep Holla , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v5] arm64: smccc: Support SMCCC v1.3 SVE register saving hint In-Reply-To: <20210601130419.5432-1-broonie@kernel.org> References: <20210601130419.5432-1-broonie@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: broonie@kernel.org, catalin.marinas@arm.com, will@kernel.org, lorenzo.pieralisi@arm.com, sudeep.holla@arm.com, ardb@kernel.org, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210601_065832_631787_A483DDB8 X-CRM114-Status: GOOD ( 24.47 ) 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 Tue, 01 Jun 2021 14:04:19 +0100, Mark Brown wrote: > > SMCCC v1.2 requires that all SVE state be preserved over SMC calls which > introduces substantial overhead in the common case where there is no SVE > state in the registers. To avoid this SMCCC v1.3 introduces a flag which > allows the caller to say that there is no state that needs to be preserved > in the registers. Make use of this flag, setting it if the SMCCC version > indicates support for it and the TIF_ flags indicate that there is no live > SVE state in the registers, this avoids placing any constraints on when > SMCCC calls can be done or triggering extra saving and reloading of SVE > register state in the kernel. > > This would be straightforward enough except for the rather entertaining > inline assembly we use to do SMCCC v1.1 calls to allow us to take advantage > of the limited number of registers it clobbers. Deal with this by having a > function which we call immediately before issuing the SMCCC call to make > our checks and set the flag. Using alternatives the overhead if SVE is > supported but not detected at runtime can be reduced to a single NOP. > > Signed-off-by: Mark Brown > Reviewed-by: Ard Biesheuvel Reviewed-by: Marc Zyngier M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel