From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D2E13BC4EF; Wed, 21 Jan 2026 13:56:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769003788; cv=none; b=aisVROiIHgTv0jraIsBsqbmvWCelppldxbYrUbU/24rNN3y4/UaG54rwoZxVqL+McjOrhRZmZTLK95VbcYoxFL9tEuwwq+XEwpbUilRLScHdYi310nzb/nsyUXi1hDynUbowNnhUISac5iTcncIvX9CFzMOjaEMlsCLji23oKow= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769003788; c=relaxed/simple; bh=lbBz6UOMJpiAg21QC6WCb59iTGSeHK+XaQZanHQt5+8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Bl1TaN/kBUcGF/n7BRrKnjzFv6RmhI6QQ1bj39VxS71CA3R10BT8ralO0lJzr0ZBNAuozWy5JqOcDY1WRsxg2B/q5fCRFcO6+AdmLEHsvqoSvUjbrHW63kDitwDo9irWKrg74SyJl+DzOrtEHjx/5OqUtxeYnuT2ieY1PIDhRHs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T7BMdWss; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="T7BMdWss" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6934CC4CEF1; Wed, 21 Jan 2026 13:56:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769003787; bh=lbBz6UOMJpiAg21QC6WCb59iTGSeHK+XaQZanHQt5+8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=T7BMdWsscuprZQVqjgOlNMHQ95GLHAGfSruDk8Hm1EMwxIKP96InkuM3UMB7u5rYV HmvbfCjC3dF3OtyAqUAGXRrOEG+6qNhEap/BNJSlBkGCK4BHHWr9hqNpbxq+i6IO0T 2ihErp/aMr/i01amz4uGoEOIRafJCwUjPZiVZSYo/r3Sp++Ui8WJJsESZqSn4SxkdN JhO7HLuehfbTUyTtffFTnlW4eHwvTQANZr0qQrnavK1cDJa6e27sMJdmuGVwAGVsMN ReeS9iIu+0tK0KErkKI0/LYvUkmH2uwk2TY/Oca1gdt6kwb5t7T3NWjrgzaMam25hx 0bNTu3WicJiGA== Date: Wed, 21 Jan 2026 13:56:20 +0000 From: Will Deacon To: Yeoreum Yun Cc: Mark Rutland , Marc Zyngier , catalin.marinas@arm.com, broonie@kernel.org, oliver.upton@linux.dev, miko.lenczewski@arm.com, kevin.brodsky@arm.com, ardb@kernel.org, suzuki.poulose@arm.com, lpieralisi@kernel.org, yangyicong@hisilicon.com, scott@os.amperecomputing.com, joey.gouly@arm.com, yuzenghui@huawei.com, pbonzini@redhat.com, shuah@kernel.org, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v11 RESEND 9/9] arm64: armv8_deprecated: apply FEAT_LSUI for swpX emulation. Message-ID: References: <20251214112248.901769-1-yeoreum.yun@arm.com> <20251214112248.901769-10-yeoreum.yun@arm.com> <86ms3knl6s.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jan 20, 2026 at 05:59:47PM +0000, Yeoreum Yun wrote: > On second thought, while a CPU that implements LSUI is unlikely to > support AArch32 compatibility, > I don't think LSUI requires the absence of AArch32. > These two are independent features (and in fact our FVP reports/supports both). Did you have to configure the FVP specially for this or that a "default" configuration? > Given that, I'm not sure a WARN is really necessary. > Would it be sufficient to just drop the patch for swpX instead? Given that the whole point of LSUI is to remove the PAN toggling, I think we should make an effort to make sure that we don't retain PAN toggling paths at runtime that could potentially be targetted by attackers. If we drop the SWP emulation patch and then see that we have AArch32 at runtime, we should forcefully disable the SWP emulation but, since we don't actually think we're going to see this in practice, the WARN seemed simpler. Will