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 BF8C1C19F2E for ; Thu, 27 Feb 2025 10:57:15 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=3HmQt5p8F2N1Emr15p2JRIq13zA8dEDAibe87C49Mc8=; b=n2hj7mXCyrEzRfrqgczvEV32pt XKT/daJijKPZoNvCzmbfm0xX3FA9ChnrRlZ4RG86uDdwVluBLpl8wMfC1gOH4sRh5eI0zGGgqAQ8j 5lnYxdnHrTy7FzTXZkem7B+h4Wlk3rF/XzoNEVkQCTo4r7/5k6y7GmNdbAVBNnoSBTmSmeEi+Ehqn 73vG3sHIUhzPQt9bWUJa0QnNsHdKveSMEmdqFMfyFLdzFZx/DxltIzyYgb9g4yUKb8/zgPT1m05OW fYLpGJCUSs7RIgVXu4m5FKP4Du8dghyUqdg6R42drvl+6QWL4vZuVAM6Dxe3m8LE/Wwb9/UcVCfW4 3yXacDgg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tnbZj-000000073xk-1VmP; Thu, 27 Feb 2025 10:57:07 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tnbXn-000000073TZ-13Ds for linux-arm-kernel@lists.infradead.org; Thu, 27 Feb 2025 10:55:07 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 3F66E613A3; Thu, 27 Feb 2025 10:54:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0075C4CEDD; Thu, 27 Feb 2025 10:55:02 +0000 (UTC) Date: Thu, 27 Feb 2025 10:55:00 +0000 From: Catalin Marinas To: Will Deacon Cc: Steven Price , "Aneesh Kumar K . V" , Suzuki K Poulose , Marc Zyngier , James Morse , Oliver Upton , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Gavin Shan , Shanker Donthineni , Alper Gun , kvmarm@lists.linux.dev, kvm@vger.kernel.org Subject: Re: [PATCH v7 09/11] arm64: Enable memory encrypt for Realms Message-ID: References: <20241017131434.40935-1-steven.price@arm.com> <20241017131434.40935-10-steven.price@arm.com> <5aeb6f47-12be-40d5-be6f-847bb8ddc605@arm.com> <20250227002330.GA24899@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250227002330.GA24899@willie-the-truck> 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 Thu, Feb 27, 2025 at 12:23:31AM +0000, Will Deacon wrote: > On Wed, Feb 26, 2025 at 07:03:01PM +0000, Catalin Marinas wrote: > > On Wed, Feb 19, 2025 at 02:30:28PM +0000, Steven Price wrote: > > > > @@ -23,14 +25,16 @@ bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED > > > > bool can_set_direct_map(void) > > > > { > > > > /* > > > > - * rodata_full and DEBUG_PAGEALLOC require linear map to be > > > > - * mapped at page granularity, so that it is possible to > > > > + * rodata_full, DEBUG_PAGEALLOC and a Realm guest all require linear > > > > + * map to be mapped at page granularity, so that it is possible to > > > > * protect/unprotect single pages. > > > > * > > > > * KFENCE pool requires page-granular mapping if initialized late. > > > > + * > > > > + * Realms need to make pages shared/protected at page granularity. > > > > */ > > > > return rodata_full || debug_pagealloc_enabled() || > > > > - arm64_kfence_can_set_direct_map(); > > > > + arm64_kfence_can_set_direct_map() || is_realm_world(); > > > > } > > > > > > Aneesh pointed out that this call to is_realm_world() is now too early > > > since the decision to delay the RSI detection. The upshot is that a > > > realm guest which doesn't have page granularity forced for other reasons > > > will fail to share pages with the host. > > > > > > At the moment I can think of a couple of options: > > > > > > (1) Make rodata_full a requirement for realm guests. > > > CONFIG_RODATA_FULL_DEFAULT_ENABLED is already "default y" so this > > > isn't a big ask. > > > > > > (2) Revisit the idea of detecting when running as a realm guest early. > > > This has the advantage of also "fixing" earlycon (no need to > > > manually specify the shared-alias of an unprotected UART). > > > > > > I'm currently leaning towards (1) because it's the default anyway. But > > > if we're going to need to fix earlycon (or indeed find other similar > > > issues) then (2) would obviously make sense. > > > > I'd go with (1) since the end result is the same even if we implemented > > (2) - i.e. we still avoid block mappings in realms. > > Is it, though? The config option is about the default behaviour but there's > still an "rodata=" option on the command-line. Yeah, that's why I suggested the pr_err() to only state that it cannot set the direct map and consider rodata=full rather than a config option. We already force CONFIG_STRICT_KERNEL_RWX. But we can also revisit the decision not to probe the RSI early. -- Catalin