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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E625BC433F5 for ; Tue, 23 Nov 2021 12:33:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236694AbhKWMge (ORCPT ); Tue, 23 Nov 2021 07:36:34 -0500 Received: from mail.kernel.org ([198.145.29.99]:38584 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235366AbhKWMgd (ORCPT ); Tue, 23 Nov 2021 07:36:33 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8E78A6102A; Tue, 23 Nov 2021 12:33:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637670805; bh=qeoJNcSgbBVk7r1DYK17Di/fl8glCyyr/Yvfx5GDx/c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TX5eiN6+XilYYUL2SB8jn4QVFlWbUuHBQjnohU3/wSIUZw98IL2SZkakd5+SusLcf HRhThGUf5UAlOhNFUJri/JFoZcG06SNeE+NrvgvyPzG0+1sMWgLilRoWt7qDke/ujd vA1ezHAHjXGtHgbbijftkUuyf1PufTW4F1DvduD1jWCKIEtEGSTfW1NsjCMESu9jBo aivRIRZnjVzR9s71dwl8+hRT+pFJuJ3/k8UpgVYZjta2uglXn6yuPLAyFs7wUuygqa Pcm2F9GlX2vMOJ80YCUuWRFlnfvtIhZ5hxL+M8es3q2542A/Ch1Q1xn4xAbsTO6wjN wPxhsFIFLFQgA== Date: Tue, 23 Nov 2021 12:33:20 +0000 From: Mark Brown To: Marc Zyngier Cc: Zenghui Yu , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, James Morse , Suzuki K Poulose , Alexandru Elisei , Quentin Perret , Will Deacon , kernel-team@android.com Subject: Re: [PATCH v2 2/5] KVM: arm64: Get rid of host SVE tracking/saving Message-ID: References: <20211028111640.3663631-1-maz@kernel.org> <20211028111640.3663631-3-maz@kernel.org> <5ab3836f-2b39-2ff5-3286-8258addd01e4@huawei.com> <871r38dvyr.wl-maz@kernel.org> <87v90kcb8u.wl-maz@kernel.org> <87mtlvchbe.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="q//FCEjhiy9XzDIz" Content-Disposition: inline In-Reply-To: <87mtlvchbe.wl-maz@kernel.org> X-Cookie: A closed mouth gathers no foot. Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org --q//FCEjhiy9XzDIz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Nov 23, 2021 at 10:11:33AM +0000, Marc Zyngier wrote: > Mark Brown wrote: > > We don't need to change the ABI, the ABI just says we zero the registers > > that aren't shared with FPSIMD. Instead of doing that on taking a SVE > > access trap to reenable SVE after having disabled TIF_SVE we could do > That's not the point I'm trying to make. > Userspace expects to have lost SVE information over a syscall (even if > the VL is 128, it expects to have lost P0..P15 and FFR). How do you > plan to tell userspace that this behaviour has changed? My point is that this doesn't need to change. Userspace can't tell if we zeroed the non-shared state on syscall or on some later access trap. --q//FCEjhiy9XzDIz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmGc348ACgkQJNaLcl1U h9A32Qf/Q7Q5jbrsFshgkZUBzFoqpvW0snt8h5uAD6T9O2p4YA5CaPXHdfHWiLIQ iQqziZPS0Yz6EMaiwfIx6BKYzWacpwT/k3uKbyT3tUxaWo9y7XrDrAqyqlBr24Zi XUAcppKtKYkugRLQ2aLWEjxA5x3lv2N5yK5xvRLeP+ogP1k5HPfJsU82fG81Kh17 zXksTe5o+AlSttOE25+UAcO7tUkY0OxorMjdaF+ih7OCiZlXn30dNheNniPRzxP8 +3M6ZchCoNcFNETThDNGvg+9Kt3TACRFYQsHRJk6fq4mIw9VLkVv3n93vhgzFK5n pVgD3/8+7m+I7Bj5iObRveR1nxSLaQ== =3P0L -----END PGP SIGNATURE----- --q//FCEjhiy9XzDIz--