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 mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02EAFC433EF for ; Wed, 23 Feb 2022 15:40:51 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8B71E4C613; Wed, 23 Feb 2022 10:40:51 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Xa5h4l+WPp2o; Wed, 23 Feb 2022 10:40:50 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 05BC34C5C7; Wed, 23 Feb 2022 10:40:50 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4967B4B235 for ; Wed, 23 Feb 2022 10:40:48 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ewoCuI38F0g3 for ; Wed, 23 Feb 2022 10:40:46 -0500 (EST) Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id DA0AC4B308 for ; Wed, 23 Feb 2022 10:40:46 -0500 (EST) 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 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> Cc: Basant Kumar Dwivedi , Will Deacon , Luis Machado , Szabolcs Nagy , Marc Zyngier , Shuah Khan , linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org, Alan Hayward , Shuah Khan , kvmarm@lists.cs.columbia.edu, Salil Akerkar X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm