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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 772FAC531DF for ; Tue, 20 Aug 2024 09:55:22 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Wp4Zx01z9z2xdR; Tue, 20 Aug 2024 19:55:21 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=217.140.110.172 Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=joey.gouly@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4Wp4Zw5bPpz2xQ8 for ; Tue, 20 Aug 2024 19:55:20 +1000 (AEST) 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 50B44DA7; Tue, 20 Aug 2024 02:55:15 -0700 (PDT) Received: from e124191.cambridge.arm.com (e124191.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 532323F66E; Tue, 20 Aug 2024 02:54:46 -0700 (PDT) Date: Tue, 20 Aug 2024 10:54:41 +0100 From: Joey Gouly To: Catalin Marinas Cc: Dave Martin , linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, aneesh.kumar@kernel.org, aneesh.kumar@linux.ibm.com, bp@alien8.de, broonie@kernel.org, christophe.leroy@csgroup.eu, dave.hansen@linux.intel.com, hpa@zytor.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, maz@kernel.org, mingo@redhat.com, mpe@ellerman.id.au, naveen.n.rao@linux.ibm.com, npiggin@gmail.com, oliver.upton@linux.dev, shuah@kernel.org, szabolcs.nagy@arm.com, tglx@linutronix.de, will@kernel.org, x86@kernel.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v4 18/29] arm64: add POE signal support Message-ID: <20240820095441.GA688664@e124191.cambridge.arm.com> References: <20240503130147.1154804-19-joey.gouly@arm.com> <20240801155441.GB841837@e124191.cambridge.arm.com> <20240806103532.GA1986436@e124191.cambridge.arm.com> <20240806143103.GB2017741@e124191.cambridge.arm.com> <20240815131815.GA3657684@e124191.cambridge.arm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Post: List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Aug 19, 2024 at 06:09:06PM +0100, Catalin Marinas wrote: > On Thu, Aug 15, 2024 at 04:09:26PM +0100, Dave P Martin wrote: > > On Thu, Aug 15, 2024 at 02:18:15PM +0100, Joey Gouly wrote: > > > That's a lot of words to say, or ask, do you agree with the approach of only > > > saving POR_EL0 in the signal frame if num_allocated_pkeys() > 1? > > > > > > Thanks, > > > Joey > > > > ...So..., given all the above, it is perhaps best to go back to > > dumping POR_EL0 unconditionally after all, unless we have a mechanism > > to determine whether pkeys are in use at all. > > Ah, I can see why checking for POR_EL0_INIT is useful. Only checking for > the allocated keys gets confusing with pkey 0. > > Not sure what the deal is with pkey 0. Is it considered allocated by > default or unallocatable? If the former, it implies that pkeys are > already in use (hence the additional check for POR_EL0_INIT). In > principle the hardware allows us to use permissions where the pkeys do > not apply but we'd run out of indices and PTE bits to encode them, so I > think by default we should assume that pkey 0 is pre-allocated. > > You can consider pkey 0 allocated by default. You can actually pkey_free(0), there's nothing stopping that. > So I agree that it's probably best to save it unconditionally. Alright, will leave it as is! Thanks, Joey