From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 95327345751 for ; Mon, 22 Jun 2026 18:38:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782153530; cv=none; b=AhdOEJgJtxC4Jxrt/aYaCTOmuYlB41HkY5KSI660UC3k975JCiK75P4lsQmirCVIX7knjL5E3vBdHjjpLdjlC+kWef6IIal0G/aXyLtcQQ2zfJ+lldXmtUiyAOsB+L/g6E9F9P96yS9SPpHLa3Rh3m27+gIm3BDZvKwShdfc8ig= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782153530; c=relaxed/simple; bh=RRph28hvIj0U2EgVNpb5odnyrIMXIpOtmlJ7wMuJ1qc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hql3u+X0c33sQLAYVP2uMIuCUHyr5CcIW/19YPDbnZ3LWirSDzkSSY6miIuXL/8U4xndMgoCk4kkiBDS6wsH/H6aX1ruVVPs8iZoUx+vPkzVXdmT6FkP0ioDpRhnHo2KL/0t6VcLhCzUP4Kja49jwXLRDNPYDCuyUhzozjxhpzA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Sg5UF9ai; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Sg5UF9ai" 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 Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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