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 AFEA8C433F5 for ; Wed, 23 Feb 2022 15:42:04 +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=qEIL0yjNCqlDZfp2LLZq9YM6O8kY8wxotiJnpYDtL70=; b=EDLIRqucQmD7Ep TOHOYuCKFHQizRK9kT1FgZ92cPf8XRGTZCcg+TkEf0606xRXwB0EMypS6h4BmbypmMYEwpQ1llfyO oDD5ytWQV9IniJN1mqqcXnIbmarT1a22MgrPd5lWLcPr+n6KkH18DsCbjKjclcHhSemDa1oNjBSRe hyW5CSuWr6vK0HEzkYLfXvbBTwWMRoDN62xAbobhQNcKLKjHpp18HNALieB1UPXHv5ZAUAj24V6Rz D9EVCz2KYVNitMnJq62jjz5sBvL5VoGahdBWuveEJjf43jMvPm10Gk3EqcwwxAcvDHcu/K7oai9t1 rqO/MeNY4ZXKxqLA8r8A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMtl6-00F5Hg-65; Wed, 23 Feb 2022 15:40:52 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMtl1-00F5Gm-VL for linux-arm-kernel@lists.infradead.org; Wed, 23 Feb 2022 15:40:49 +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 7B97BB820C9; Wed, 23 Feb 2022 15:40:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1019CC340E7; Wed, 23 Feb 2022 15:40:40 +0000 (UTC) Date: Wed, 23 Feb 2022 15:40:37 +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 v11 28/40] KVM: arm64: Handle SME host state when running guests Message-ID: References: <20220207152109.197566-1-broonie@kernel.org> <20220207152109.197566-29-broonie@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220207152109.197566-29-broonie@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220223_074048_388495_86A43E5F X-CRM114-Status: GOOD ( 19.43 ) 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 Mon, Feb 07, 2022 at 03:20:57PM +0000, Mark Brown wrote: > While we don't currently support SME in guests we do currently support it > for the host system so we need to take care of SME's impact, including > the floating point register state, when running guests. Simiarly to SVE > we need to manage the traps in CPACR_RL1, what is new is the handling of > streaming mode and ZA. > > Normally we defer any handling of the floating point register state until > the guest first uses it however if the system is in streaming mode FPSIMD > and SVE operations may generate SME traps which we would need to distinguish > from actual attempts by the guest to use SME. Rather than do this for the > time being if we are in streaming mode when entering the guest we force > the floating point state to be saved immediately and exit streaming mode, > meaning that the guest won't generate SME traps for supported operations. > > We could handle ZA in the access trap similarly to the FPSIMD/SVE state > without the disruption caused by streaming mode but for simplicity > handle it the same way as streaming mode for now. > > This will be revisited when we support SME for guests (hopefully before SME > hardware becomes available), for now it will only incur additional cost on > systems with SME and even there only if streaming mode or ZA are enabled. > > 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