From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kselftest-owner@kernel.org>
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 EF1E1C433EF
	for <linux-kselftest@archiver.kernel.org>; Tue, 22 Feb 2022 12:53:22 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S229436AbiBVMxq (ORCPT
        <rfc822;linux-kselftest@archiver.kernel.org>);
        Tue, 22 Feb 2022 07:53:46 -0500
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54452 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S229524AbiBVMxp (ORCPT
        <rfc822;linux-kselftest@vger.kernel.org>);
        Tue, 22 Feb 2022 07:53:45 -0500
Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3116128DC5
        for <linux-kselftest@vger.kernel.org>; Tue, 22 Feb 2022 04:53:20 -0800 (PST)
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 72465B81998
        for <linux-kselftest@vger.kernel.org>; Tue, 22 Feb 2022 12:53:19 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 248D4C340E8;
        Tue, 22 Feb 2022 12:53:14 +0000 (UTC)
Date:   Tue, 22 Feb 2022 12:53:11 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Mark Brown <broonie@kernel.org>
Cc:     Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Shuah Khan <shuah@kernel.org>,
        Alan Hayward <alan.hayward@arm.com>,
        Luis Machado <luis.machado@arm.com>,
        Salil Akerkar <Salil.Akerkar@arm.com>,
        Basant Kumar Dwivedi <Basant.KumarDwivedi@arm.com>,
        Szabolcs Nagy <szabolcs.nagy@arm.com>,
        James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-kselftest@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH v11 16/40] arm64/sme: Implement streaming SVE context
 switching
Message-ID: <YhTct2Cy1fMOsjuZ@arm.com>
References: <20220207152109.197566-1-broonie@kernel.org>
 <20220207152109.197566-17-broonie@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220207152109.197566-17-broonie@kernel.org>
Precedence: bulk
List-ID: <linux-kselftest.vger.kernel.org>
X-Mailing-List: linux-kselftest@vger.kernel.org

On Mon, Feb 07, 2022 at 03:20:45PM +0000, Mark Brown wrote:
> When in streaming mode we need to save and restore the streaming mode
> SVE register state rather than the regular SVE register state. This uses
> the streaming mode vector length and omits FFR but is otherwise identical,
> if TIF_SVE is enabled when we are in streaming mode then streaming mode
> takes precedence.
> 
> This does not handle use of streaming SVE state with KVM, ptrace or
> signals. This will be updated in further patches.

I think I get this but a state diagram somewhere would help ;).

IIUC you don't disable SM on a context switch, you just leave it in
place until a task_fpsimd_load(). It shouldn't be a problem as
kernel_neon_begin() disables it anyway.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>