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 46C27C433FE for ; Fri, 22 Apr 2022 16:28:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381488AbiDVQbF (ORCPT ); Fri, 22 Apr 2022 12:31:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59838 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241617AbiDVQbF (ORCPT ); Fri, 22 Apr 2022 12:31:05 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60E805EDD8 for ; Fri, 22 Apr 2022 09:28:11 -0700 (PDT) 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 25132B831AE for ; Fri, 22 Apr 2022 16:28:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D57AEC385A4; Fri, 22 Apr 2022 16:28:05 +0000 (UTC) Date: Fri, 22 Apr 2022 17:28:02 +0100 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 , Luca Salabrino , linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org, kvmarm@lists.cs.columbia.edu Subject: Re: [PATCH v14 16/39] arm64/sme: Implement traps and syscall handling for SME Message-ID: References: <20220419112247.711548-1-broonie@kernel.org> <20220419112247.711548-17-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220419112247.711548-17-broonie@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Tue, Apr 19, 2022 at 12:22:24PM +0100, Mark Brown wrote: > By default all SME operations in userspace will trap. When this happens > we allocate storage space for the SME register state, set up the SVE > registers and disable traps. We do not need to initialize ZA since the > architecture guarantees that it will be zeroed when enabled and when we > trap ZA is disabled. > > On syscall we exit streaming mode if we were previously in it and ensure > that all but the lower 128 bits of the registers are zeroed while > preserving the state of ZA. This follows the aarch64 PCS for SME, ZA > state is preserved over a function call and streaming mode is exited. > Since the traps for SME do not distinguish between streaming mode SVE > and ZA usage if ZA is in use rather than reenabling traps we instead > zero the parts of the SVE registers not shared with FPSIMD and leave SME > enabled, this simplifies handling SME traps. If ZA is not in use then we > reenable SME traps and fall through to normal handling of SVE. > > Signed-off-by: Mark Brown Re-adding my reviewed-by following the update. Reviewed-by: Catalin Marinas