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 62B9210ED679 for ; Fri, 27 Mar 2026 13:56:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=WCss18sy6f8aOP99Nk+4QmSSu+zP78Vtv2kjNibzlRU=; b=AsgGpmlRTveGy9KOTh5kFg+NXc fjxMTLiJrCjnbSUtEJaAic1+/FkdEvv4N6styYXZpxCVR+5jxoRCm2SO+APjgMkKn1hJJcjkA/JWw uIAgAgK2zUr1vmfdLOcqCYrl2kMwEevgeRxDSQ5tPTT/hCg+BJT9N9VeVNdLtyzfXoWVp79U0cRk+ mCxZZ/BobnCKcJ4xDpQqBMFrBq+3S36U0d4UxCy7XQ9o90NSMhrsRK9faDkZ6etMW9MNBjVxQSlNd lI1EcwJXwKnpd1m8MjevHNVtzRMxYmHrl0CMvNL6NSGXr4pBFHlhQ2lYn1ospbWkwIFBw+I5rKHr3 jNsr1tHw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w67fh-00000007UW8-38Jk; Fri, 27 Mar 2026 13:56:21 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w67fe-00000007UUW-311C for linux-arm-kernel@lists.infradead.org; Fri, 27 Mar 2026 13:56:20 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 26DCE15A1; Fri, 27 Mar 2026 06:56:10 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.1.197.6]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8DDB63F99C; Fri, 27 Mar 2026 06:56:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1774619776; bh=WCss18sy6f8aOP99Nk+4QmSSu+zP78Vtv2kjNibzlRU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ch1QomEW70t+DRrnli8fMm69HGPNma+E9iROlZi7nQwaoX6dUOQ2JtWnRSIdpGqg7 fZSIz7auQeuccyoYEIQo10XRwAP4aihUy6i1bGlld6hD18OxpUTK41orhRrdaSB5fV nr9RhTZJNZx6SnSUjSgZiRXnR7ex2+tuAeEXGGxQ= Date: Fri, 27 Mar 2026 13:56:11 +0000 From: Yeoreum Yun To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, will@kernel.org, maz@kernel.org, oupton@kernel.org, miko.lenczewski@arm.com, kevin.brodsky@arm.com, broonie@kernel.org, ardb@kernel.org, suzuki.poulose@arm.com, lpieralisi@kernel.org, joey.gouly@arm.com, yuzenghui@huawei.com Subject: Re: (subset) [PATCH v17 0/8] support FEAT_LSUI Message-ID: References: <20260314175133.1084528-1-yeoreum.yun@arm.com> <177461632621.2272468.5197255307509898250.b4-ty@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <177461632621.2272468.5197255307509898250.b4-ty@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260327_065618_972319_1D13CE7E X-CRM114-Status: GOOD ( 12.71 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Catalin, > On Sat, 14 Mar 2026 17:51:25 +0000, Yeoreum Yun wrote: > > Since Armv9.6, FEAT_LSUI supplies the load/store instructions for > > previleged level to access to access user memory without clearing > > PSTATE.PAN bit. > > > > This patchset support FEAT_LSUI and applies it mainly in > > futex atomic operation and others. > > > > [...] > > Applied to arm64 (for-next/feat_lsui), thanks! Thanks! > > I decided to drop patch [6/8] (arm64: armv8_deprecated: disable swp > emulation when FEAT_LSUI present). The way FEAT_LSUI support looks now, > we still have uaccess_enable_privileged() working properly and we could > even support SWP emulation using exclusives. While it's highly unlikely > to see both 32-bit EL0 and FEAT_LSUI in practice, This is one of decisive reason to drop the swp emulation with LSUI (https://lore.kernel.org/all/aXDbBKhE1SdCW6q4@willie-the-truck/) However, > models may support the > combination and disabling SWP emulation feels pretty artificial. But I'm not sure this is a sufficient rationale for supporting SWP with LSUI, since it's highly unlikely to encounter a real CPU that supports both 32-bit EL0 and FEAT_LSUI. Anyway, it's fair enough to drop 6/8 right now. But I appreciate whether it would be good to support SWP emulation with LSUI so that let me respin for it with the former patch. [...] -- Sincerely, Yeoreum Yun