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 0AC69C07CB1 for ; Wed, 29 Nov 2023 10:46:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=VcTGv56oau2ctbsOQ2tP8rNDcOx3x1Zpx9rhrpUFDmM=; b=vBZCgWLqIZFgEu qha/DbYpfT6fYvS7FZH8fz6Y6XwK9WNpRisriCIS/RVJHgTrfiqpNOWXCp6CVHgq7p5YMCAg5G06F v5TEeEpMjVlGUI5y4SkHbhroLR7BJL7NwimJEQK4AKN7/RZQBliYdn8512HEHagraQrr/NACkYAJB aHGT8kMgVAyD/np3u/WCwdd15qXRvP3kewB6WilDg8bIevEwVpixxQcinrSinqnqn7WdiAiWL6b9U U5FSoSzKimQUgLv+WItwnwl8LDQXZl8gJNR3VVktXg5/MK4KMIHMllawG6wIAuLeAoq/6kke/P5bS hqKXQbncFgw4vIzSmONw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r8I5D-007rQJ-2P; Wed, 29 Nov 2023 10:46:19 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r8I5A-007rPI-1F for linux-arm-kernel@lists.infradead.org; Wed, 29 Nov 2023 10:46:17 +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 EEA3E2F4; Wed, 29 Nov 2023 02:47:00 -0800 (PST) Received: from raptor (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 857663F5A1; Wed, 29 Nov 2023 02:46:08 -0800 (PST) Date: Wed, 29 Nov 2023 10:46:05 +0000 From: Alexandru Elisei To: David Hildenbrand Cc: catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org, rppt@kernel.org, hughd@google.com, pcc@google.com, steven.price@arm.com, anshuman.khandual@arm.com, vincenzo.frascino@arm.com, eugenis@google.com, kcc@google.com, hyesoo.yu@samsung.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH RFC v2 13/27] arm64: mte: Make tag storage depend on ARCH_KEEP_MEMBLOCK Message-ID: References: <20231119165721.9849-1-alexandru.elisei@arm.com> <20231119165721.9849-14-alexandru.elisei@arm.com> <91c5d2e2-57b1-4172-88e0-cd07a8d85af4@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231129_024616_543450_8582F99C X-CRM114-Status: GOOD ( 35.23 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Tue, Nov 28, 2023 at 06:05:20PM +0100, David Hildenbrand wrote: > On 27.11.23 16:04, Alexandru Elisei wrote: > > Hi, > > > > On Fri, Nov 24, 2023 at 08:51:38PM +0100, David Hildenbrand wrote: > > > On 19.11.23 17:57, Alexandru Elisei wrote: > > > > Tag storage memory requires that the tag storage pages used for data are > > > > always migratable when they need to be repurposed to store tags. > > > > > > > > If ARCH_KEEP_MEMBLOCK is enabled, kexec will scan all non-reserved > > > > memblocks to find a suitable location for copying the kernel image. The > > > > kernel image, once loaded, cannot be moved to another location in physical > > > > memory. The initialization code for the tag storage reserves the memblocks > > > > for the tag storage pages, which means kexec will not use them, and the tag > > > > storage pages can be migrated at any time, which is the desired behaviour. > > > > > > > > However, if ARCH_KEEP_MEMBLOCK is not selected, kexec will not skip a > > > > region unless the memory resource has the IORESOURCE_SYSRAM_DRIVER_MANAGED > > > > flag, which isn't currently set by the tag storage initialization code. > > > > > > > > Make ARM64_MTE_TAG_STORAGE depend on ARCH_KEEP_MEMBLOCK to make it explicit > > > > that that the Kconfig option required for it to work correctly. > > > > > > > > Signed-off-by: Alexandru Elisei > > > > --- > > > > arch/arm64/Kconfig | 1 + > > > > 1 file changed, 1 insertion(+) > > > > > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > > index 047487046e8f..efa5b7958169 100644 > > > > --- a/arch/arm64/Kconfig > > > > +++ b/arch/arm64/Kconfig > > > > @@ -2065,6 +2065,7 @@ config ARM64_MTE > > > > if ARM64_MTE > > > > config ARM64_MTE_TAG_STORAGE > > > > bool "Dynamic MTE tag storage management" > > > > + depends on ARCH_KEEP_MEMBLOCK > > > > select CONFIG_CMA > > > > help > > > > Adds support for dynamic management of the memory used by the hardware > > > > > > Doesn't arm64 select that unconditionally? Why is this required then? > > > > I've added this patch to make the dependancy explicit. If, in the future, arm64 > > stops selecting ARCH_KEEP_MEMBLOCK, I thinkg it would be very easy to miss the > > fact that tag storage depends on it. So this patch is not required per-se, it's > > there to document the dependancy. > > I see. Could you add some static_assert / BUILD_BUG_ON instead? I can do that, sure. Thanks, Alex > > I suspect there are plenty other (undocumented) reasons why > ARCH_KEEP_MEMBLOCK has to be enabled for now, and none sets > ARCH_KEEP_MEMBLOCK, I suspect/ > > -- > Cheers, > > David / dhildenb > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel