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 B1E8FCD98F2 for ; Mon, 22 Jun 2026 18:38:58 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=4gJOKgrcFuTUCEHQYsdjEclgb7VeirQAcn5Q0EzveSk=; b=brKS6x7UXcQoL3TkFdMZxWUayQ /MlaH8sRJCu/HwV3oByP7O2UdXKstFSqAR+t67deN0iBY3JeReE53bQpwJcOCiGaRwJ8MkCf5aDdu n8fEE6ro+Xs8AXNAFCbe4Fi6RtvwftfvnrGq0v5VoCsgUnInxQw+5U8w+KIB2QGcVrQ2s1/TvTekS PzNuLDD7QtswOjT4Yocb+EmFs11xUoLxpTVaNt38/lWMPLL+HkpN5FNwjoEy5xqSQQDuhd2P4zQ8+ wkx73x4rdTbiNoYI7aXiK3s1fYVYYmT3e3+OccxF5Ew5MiJlBtSKWmQmtrC1GX2Cf8qsjszBdAx4P xFvmDJGQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wbjXn-00000005IiX-1aMO; Mon, 22 Jun 2026 18:38:51 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wbjXl-00000005IiL-3XHR for linux-arm-kernel@lists.infradead.org; Mon, 22 Jun 2026 18:38:49 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 48CFC43867; Mon, 22 Jun 2026 18:38:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0A1491F000E9; Mon, 22 Jun 2026 18:38:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782153529; bh=4gJOKgrcFuTUCEHQYsdjEclgb7VeirQAcn5Q0EzveSk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Sg5UF9aie4Ukwen70Q8bPYsBeApogmGwATui9tQVae/fexhlT5kYmGLg8fxvTeArN w8EOuFXHrLlJIJvVB84baaswRBrAYrg/I3+Mprn09zh5nd81M6QecMD8KASof9wpbJ BdED5l6LbFG43rI8xEQ9W+bvFA8HF56J6enOXWuAcMW1HheE64fkyhwtsz1f39jrFJ Mr4kcqUvy2AGsoiDTUQMu9d9OC8E/92lndJfTvhkxx2xPOZan8DzlImQ3s+Z1wbedO pPmlXXCDGIShDXYZqqLkt7OVeMJxOovawYoFHkj00l9DPCX7JBLCKHEsuB6x4ayzCR m03K3XGq6qW1g== Message-ID: <9b11b0c0-dfc7-45ba-934e-19cd053e5635@kernel.org> Date: Mon, 22 Jun 2026 20:38:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v8 01/24] mm: Introduce kpkeys To: Linus Walleij Cc: Kevin Brodsky , linux-hardening@vger.kernel.org, Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Lorenzo Stoakes , Thomas Gleixner References: <20260526-kpkeys-v8-0-eaaacdacc67c@arm.com> <20260526-kpkeys-v8-1-eaaacdacc67c@arm.com> <70f4dcdf-c45f-47d3-91df-a7897bd86ff4@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit 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 On 6/18/26 15:22, Linus Walleij wrote: > On Tue, Jun 16, 2026 at 5:19 PM David Hildenbrand (Arm) > wrote: > >> Looking at this, and wondering about "why do we get registers involved in this >> API" I would probably have an interface like: >> >> arch_kpkeys_enter_context() >> arch_kpkeys_leave_context() >> >> Whereby you return a "struct kpkeys_state" or sth like that. > > This is close to what I was looking for as well. Cool :) > > enter/leave makes the code look more like generic entry. > > Passing some kind of state cookie around is inevitable in > this design and IIUC Kevin argued that it would be inefficient > (another level of abstraction) as opposed to just hammering > in the context we want, where we want it. > > But I think the compiler will optimize that out by constant > propagation if the backing architecture implementation is > simple. Yes, it should be wrapped somehow. I don't think this will be a problem performance-wise that cannot be solved differently. Returning an u64 ("register") here is really arm64-sepcific and should be abstracted. -- Cheers, David