From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B3BBF606A319 for ; Wed, 21 Oct 2026 09:58:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=m7tlYOJD; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=DRkcpboT 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=cz8+V7XCKKhBDpf80aiJInY1iYNOWN4+wC7qm69EtcE=; b=m7tlYOJDSQTBUAViVB0quaIH2r R4DiehncHFII4XRRShuEK/0zC3WyunObS1fPBYRgfC/g0KCELu+r1X5HjFesv374KjrpvccjS+y0B GACclxX1sn03s/8CBkfbHEhl8say82WiHCp/JaQI8qJmqbT7HuEbjOQ1jnea8EXfBFn23GeYma6CV LVnmCbpu4VHJMZaGqQ9mHw86dS6QRzlmPV3MOH3IjxNNRsBxTYvTgZru5eh3BMBgstiEhZubICKVO hnFw+KOsX8A1aBtBl4kccEBXYrxuQ0Rc+Yg6Nb9bAqkwD5snQI5Iopma8NO+aXJ1fDGFilmDF8wJG RVnrfnbA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xJT5T-0000000BYDu-2HVG; Wed, 21 Oct 2026 09:58:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xJT5Q-0000000BYD0-1v3L for linux-arm-kernel@lists.infradead.org; Wed, 21 Oct 2026 09:58:21 +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 75B8216F8; Wed, 21 Oct 2026 02:58:14 -0700 (PDT) Received: from [10.2.197.99] (ewhatever.cambridge.arm.com [10.2.197.99]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D4FE73F7D8; Wed, 21 Oct 2026 02:58:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1792576697; bh=IDazUdpoih0dXqrNnstcGcC5WHNZlytoR2PIn318lzU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=DRkcpboTgyBklO5nuoilzcuW60prH769ubwJBYdbsa7qFkOBtmzSkDopdCyhAq/Vf 0xUBoqHSlTFtlUGpNPuruwGePjNOawfP0umRaLeQQ9ORXwAvjKwdlEFaU0NFOaBVsD x51xk7Lm3RaVhL6tF2NWgRDq+mj7fmlqjVsqiIGY= Message-ID: <5d487949-9195-442f-97af-acb9e3fdfb0d@arm.com> Date: Wed, 21 Oct 2026 10:58:13 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v19 5/7] firmware: arm_rmm: Activate the RMM To: Catalin Marinas , Marc Zyngier Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, maz@kernel.org, will@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, gshan@redhat.com, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com, sudeep.holla@arm.com, jonathan.cameron@oss.qualcomm.com References: <20260924135201.850038-1-suzuki.poulose@arm.com> <20260924135201.850038-6-suzuki.poulose@arm.com> <12e83d88-de4c-4230-aac2-1796123320ad@arm.com> <70d47475-e26e-40e1-b409-b0c16aecb8c0@arm.com> <195cdfe4-a55a-453f-9c34-620738eca244@arm.com> <0f68dcff-1dfe-4515-9912-515ca6457674@arm.com> Content-Language: en-US From: Suzuki K Poulose In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261021_025820_541360_8C3864EF X-CRM114-Status: GOOD ( 15.81 ) X-Spam-Score: -4.4 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-7.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 29/09/2026 12:15, Catalin Marinas wrote: > On Mon, Sep 28, 2026 at 07:28:20PM +0100, Suzuki K Poulose wrote: >> On 28/09/2026 19:01, Catalin Marinas wrote: >>> possible, to defer the RMM activation until the first user (still do the >>> RMI probing as an initcall). If we run on RME-capable hardware and >>> firmware but don't care about realms or TSM, we still get the normal OS >>> functionality. >> >> Would you prefer this in the first drop of the RMM ? Or is this >> something we could add as a separate series ? > > I think we could add the deferring as a separate patch, maybe together > with the KVM bits. An advantage of keeping it here if we merge this > first is that we still exercise the activation path without full realm > support or TSM. Otherwise a lot of this would be dead code until the > other series arrive. Either way, do it as as separate patch on top of > this series. > I have been looking at the "on-demand" activation support and came across the following design decision. * We have KVM_CAP_ARM_RME which advertises that KVM can create Realm VMs to the userspace. A VMM could check this before it creates a Realm VM using KVM_CREATE_VM with type=RealmVM. Now, we could delay the RMM activation as late as the KVM_CREATE_VM and kick it off while we initialise the kvm as part of kvm_arch_init_vm(). But if that fails, we would fail the KVM_CREATE_VM. The question is, what should KVM_CAP_ARM_RME indicate ? We could initially enable the cap based on the presence of RMM (but not activated). However, should we turn the KVM_CAP_ARM_RME=off when we fail to activate the RMM ? Is that senisble ? (i.e., runtime disabling a cap). Cheers Suzuki