From patchwork Fri Oct 4 14:43:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Price X-Patchwork-Id: 13822488 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8F0B22225AB; Fri, 4 Oct 2024 14:44:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728053053; cv=none; b=SYhNeMYiN31YhA/xD/Q9ELEUbvWVh7w9XFBYiVdtTvKXo7Bg/FVXTImIp6dF1DmVg6ZYDhaeMeJQCCSBtS+t2rHJfGK81V4irfUnhMKw92SHYczTrGGwRmCLZqDZB/w2Y9371iLwWnlKHsHOouw+3uGxHFe21Qcq9J2MKiZiBKc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728053053; c=relaxed/simple; bh=KEFNoLyaJ2uRSOShd+RlYUc8lknhTSllTHNVhp4YU8Q=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=MBDj8hvTh4n5BIhShC+czLrzOyFFt63hjcYw/v4QTSnvO9jkXMIYlfoUYijnBAU8U1lNLmWrdfnDt0lJ8V5XlU+3Nuc+DWv3OHMZnwUlAIzJnw45XoL6pQaLRqBGOjbRXhXkAGULWuiH6SGyadHvU/2/NxPrUcqv8juyUJmJkzk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 B89BA1063; Fri, 4 Oct 2024 07:44:40 -0700 (PDT) Received: from e122027.cambridge.arm.com (unknown [10.1.25.25]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7423F3F58B; Fri, 4 Oct 2024 07:44:07 -0700 (PDT) From: Steven Price To: kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: Steven Price , Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , 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 , "Aneesh Kumar K . V" Subject: [PATCH v6 11/11] arm64: Document Arm Confidential Compute Date: Fri, 4 Oct 2024 15:43:06 +0100 Message-Id: <20241004144307.66199-12-steven.price@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241004144307.66199-1-steven.price@arm.com> References: <20241004144307.66199-1-steven.price@arm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add some documentation on Arm CCA and the requirements for running Linux as a Realm guest. Also update booting.rst to describe the requirement for RIPAS RAM. Signed-off-by: Steven Price Reviewed-by: Gavin Shan Reviewed-by: Suzuki K Poulose --- Documentation/arch/arm64/arm-cca.rst | 67 ++++++++++++++++++++++++++++ Documentation/arch/arm64/booting.rst | 3 ++ Documentation/arch/arm64/index.rst | 1 + 3 files changed, 71 insertions(+) create mode 100644 Documentation/arch/arm64/arm-cca.rst diff --git a/Documentation/arch/arm64/arm-cca.rst b/Documentation/arch/arm64/arm-cca.rst new file mode 100644 index 000000000000..ab7f90e64c2f --- /dev/null +++ b/Documentation/arch/arm64/arm-cca.rst @@ -0,0 +1,67 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +Arm Confidential Compute Architecture +===================================== + +Arm systems that support the Realm Management Extension (RME) contain +hardware to allow a VM guest to be run in a way which protects the code +and data of the guest from the hypervisor. It extends the older "two +world" model (Normal and Secure World) into four worlds: Normal, Secure, +Root and Realm. Linux can then also be run as a guest to a monitor +running in the Realm world. + +The monitor running in the Realm world is known as the Realm Management +Monitor (RMM) and implements the Realm Management Monitor +specification[1]. The monitor acts a bit like a hypervisor (e.g. it runs +in EL2 and manages the stage 2 page tables etc of the guests running in +Realm world), however much of the control is handled by a hypervisor +running in the Normal World. The Normal World hypervisor uses the Realm +Management Interface (RMI) defined by the RMM specification to request +the RMM to perform operations (e.g. mapping memory or executing a vCPU). + +The RMM defines an environment for guests where the address space (IPA) +is split into two. The lower half is protected - any memory that is +mapped in this half cannot be seen by the Normal World and the RMM +restricts what operations the Normal World can perform on this memory +(e.g. the Normal World cannot replace pages in this region without the +guest's cooperation). The upper half is shared, the Normal World is free +to make changes to the pages in this region, and is able to emulate MMIO +devices in this region too. + +A guest running in a Realm may also communicate with the RMM to request +changes in its environment or to perform attestation about its +environment. In particular it may request that areas of the protected +address space are transitioned between 'RAM' and 'EMPTY' (in either +direction). This allows a Realm guest to give up memory to be returned +to the Normal World, or to request new memory from the Normal World. +Without an explicit request from the Realm guest the RMM will otherwise +prevent the Normal World from making these changes. + +Linux as a Realm Guest +---------------------- + +To run Linux as a guest within a Realm, the following must be provided +either by the VMM or by a `boot loader` run in the Realm before Linux: + + * All protected RAM described to Linux (by DT or ACPI) must be marked + RIPAS RAM before handing over the Linux. + + * MMIO devices must be either unprotected (e.g. emulated by the Normal + World) or marked RIPAS DEV. + + * MMIO devices emulated by the Normal World and used very early in boot + (specifically earlycon) must be specified in the upper half of IPA. + For earlycon this can be done by specifying the address on the + command line, e.g.: ``earlycon=uart,mmio,0x101000000`` + + * Linux will use bounce buffers for communicating with unprotected + devices. It will transition some protected memory to RIPAS EMPTY and + expect to be able to access unprotected pages at the same IPA address + but with the highest valid IPA bit set. The expectation is that the + VMM will remove the physical pages from the protected mapping and + provide those pages as unprotected pages. + +References +---------- +[1] https://developer.arm.com/documentation/den0137/ diff --git a/Documentation/arch/arm64/booting.rst b/Documentation/arch/arm64/booting.rst index b57776a68f15..30164fb24a24 100644 --- a/Documentation/arch/arm64/booting.rst +++ b/Documentation/arch/arm64/booting.rst @@ -41,6 +41,9 @@ to automatically locate and size all RAM, or it may use knowledge of the RAM in the machine, or any other method the boot loader designer sees fit.) +For Arm Confidential Compute Realms this includes ensuring that all +protected RAM has a Realm IPA state (RIPAS) of "RAM". + 2. Setup the device tree ------------------------- diff --git a/Documentation/arch/arm64/index.rst b/Documentation/arch/arm64/index.rst index 78544de0a8a9..12c243c3af20 100644 --- a/Documentation/arch/arm64/index.rst +++ b/Documentation/arch/arm64/index.rst @@ -10,6 +10,7 @@ ARM64 Architecture acpi_object_usage amu arm-acpi + arm-cca asymmetric-32bit booting cpu-feature-registers