From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 924993EDE63; Wed, 27 May 2026 10:03:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779876187; cv=none; b=t3bATSRo/sO/tw76Mj2mXwgOInSw9G8t+GGNzOX/5MUr83WXAjc+tcOCAmhJ5Nyd/6+9fjzKlJzVpSgMo89v8u+b/FmLIVbFB7LBu+VnLxTe4HFK9E4QuCKEKM29guzxcUjzBG/r+B8b4m/AMWSOOltqTLxgBfO41ZKFebd/Mms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779876187; c=relaxed/simple; bh=iA/6eVaIs2YRbOL8p+zvsk4lHQ7EZADkD10ncYRdudw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BFE1ymSN65niYH4/1qZiqZ8G3xgpWlszSmDLwpnBMBUXKhqAF5pCNO6iGxw73ARzr8fS+Gs9XJmHNj49ZHcXRAWV1+pOhqyapk74dvkBvoFkAMG8klS6yJoUib8fYZ6UTR3/DI9sKttJKnXSYbv+7pwtSHLP2UVql/aHBv5P8YY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oLEjgg70; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oLEjgg70" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 22DAD1F00A3A; Wed, 27 May 2026 10:03:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779876185; bh=F2nYKWWl6fKV1ODVGqLXuKiCYR5y2lxxAtCQSJik2Eo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=oLEjgg70D4yKfNEW0AHQBtlJXBKLhrhjFeYZAMGqBsEC4qwlAtJ7bUCc84eQbwQ68 K+Jn+m/wrI7KRx2SYLrAom/hWTQIxOUIcsaKzme1l5aFVAkS/AIlEnfoWJ+OrZuXnm YAJvS1m8j73P37dILaqDi6dt2AB5haGE24I2lGQt6hycxqhmxh+oQijzQrVeJsOQTA ++7dn43fpEWcxza0Owz7EVpc4uEeSq+aBgh1x7C+rrgK9PS8CxQIE6x3vqoMB4HFcG 4qJpoeKCmCyUpjuxKPf8mxbGwESdSJ9iz50gcxc02PnN4qrN35YL57Z+rtedljK1+c RaHLd7pSVF2nw== From: "Aneesh Kumar K.V (Arm)" To: linux-coco@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: "Aneesh Kumar K.V (Arm)" , Catalin Marinas , Greg KH , Jeremy Linton , Jonathan Cameron , Lorenzo Pieralisi , Mark Rutland , Sudeep Holla , Will Deacon , Steven Price , Suzuki K Poulose Subject: [PATCH v6 4/4] coco: guest: arm64: Replace dummy CCA device with sysfs ABI Date: Wed, 27 May 2026 15:32:33 +0530 Message-ID: <20260527100233.428018-5-aneesh.kumar@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260527100233.428018-1-aneesh.kumar@kernel.org> References: <20260527100233.428018-1-aneesh.kumar@kernel.org> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The SMCCC firmware driver now creates the arm-smccc platform device and instantiates the CCA RSI auxiliary devices once the RSI ABI is discovered. The arm64-specific arm-cca-dev platform device stub is therefore no longer needed. However, userspace has used the arm-cca-dev platform device to detect Arm CCA Realm guests [1]. Removing it without a replacement would break that detection and would also leave userspace depending on kernel device-model details. Add /sys/firmware/cca/realm_guest as a stable, architecture-provided ABI for detecting whether the kernel is running as an Arm CCA Realm guest. The file returns 1 in Realm world and 0 otherwise, similar to the existing s390 /sys/firmware/uv/prot_virt_guest interface for protected virtualization guests. Remove the dummy arm-cca-dev registration now that userspace has a dedicated CCA Realm guest indicator, and document the new ABI in Documentation/ABI/testing/sysfs-firmware-cca. [1] https://lore.kernel.org/all/4a7d84b2-2ec4-4773-a2d5-7b63d5c683cf@arm.com Signed-off-by: Aneesh Kumar K.V (Arm) --- Documentation/ABI/testing/sysfs-firmware-cca | 10 +++++ arch/arm64/kernel/rsi.c | 39 +++++++++++++++----- 2 files changed, 39 insertions(+), 10 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-firmware-cca diff --git a/Documentation/ABI/testing/sysfs-firmware-cca b/Documentation/ABI/testing/sysfs-firmware-cca new file mode 100644 index 000000000000..bf177d636b92 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-firmware-cca @@ -0,0 +1,10 @@ +What: /sys/firmware/cca/realm_guest +Date: May 2026 +Contact: Linux ARM Kernel Mailing list +Description: Read-only. Indicates whether the kernel is running as an + Arm Confidential Compute Architecture (CCA) Realm guest. + + The value is one of: + + 0: the kernel is not running as a Realm guest + 1: the kernel is running as a Realm guest diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c index da440f71bb64..a333029ddf08 100644 --- a/arch/arm64/kernel/rsi.c +++ b/arch/arm64/kernel/rsi.c @@ -9,6 +9,8 @@ #include #include #include +#include +#include #include #include @@ -16,6 +18,7 @@ #include static struct realm_config config; +static struct kobject *cca_kobj; unsigned long prot_ns_shared; EXPORT_SYMBOL(prot_ns_shared); @@ -160,17 +163,33 @@ void __init arm64_rsi_init(void) static_branch_enable(&rsi_present); } -static struct platform_device rsi_dev = { - .name = "arm-cca-dev", - .id = PLATFORM_DEVID_NONE +static ssize_t cca_is_realm_guest(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%d\n", is_realm_world()); +} + +static struct kobj_attribute cca_realm_guest = + __ATTR(realm_guest, 0444, cca_is_realm_guest, NULL); + +static const struct attribute *cca_realm_attrs[] = { + &cca_realm_guest.attr, + NULL, }; -static int __init arm64_create_dummy_rsi_dev(void) +static int __init realm_sysfs_init(void) { - if (is_realm_world() && - platform_device_register(&rsi_dev)) - pr_err("failed to register rsi platform device\n"); - return 0; -} + int ret; + + cca_kobj = kobject_create_and_add("cca", firmware_kobj); + if (!cca_kobj) + return -ENOMEM; -arch_initcall(arm64_create_dummy_rsi_dev) + ret = sysfs_create_files(cca_kobj, cca_realm_attrs); + if (!ret) + return 0; + + kobject_put(cca_kobj); + return ret; +} +device_initcall(realm_sysfs_init); -- 2.43.0