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 9BB63CD5BC9 for ; Wed, 27 May 2026 10:03:20 +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:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=F2nYKWWl6fKV1ODVGqLXuKiCYR5y2lxxAtCQSJik2Eo=; b=PWoSwQ2xL2ydT1E0hLPcgh7Hta JB468arU7xjHHJ3EiRxl+sGz8M38WnxtCXhSgJ8tEecAPuoaopaZxqoIdUHU1HkrC5U1ATBrYYYlY nKW8fFRmeGN0CiIr9ay3AuVQV4793yU2eQ1yOaDB+Z5TQdIO6pszdAU504cufVkXP1QQFtrWBz+7M 7kjaMYvVlmb6i881TA88dj3tre9eE59iB5fG5Q0VpCGU5HLBG+G9Aqmnii84TbabJ9uylKcGbictN 48a2KNplTS1jY9fTIfIThH4ykZWSIwzhhEaAl0eFN7rsmPfH/QK6hSKJhEWXtdleZyCNjApbBq2Xl k9my3bjg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wSB6X-00000003hkQ-1YjA; Wed, 27 May 2026 10:03:13 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wSB6P-00000003hee-2Lb6 for linux-arm-kernel@lists.infradead.org; Wed, 27 May 2026 10:03:06 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 4BDFC42A2B; Wed, 27 May 2026 10:03:05 +0000 (UTC) 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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260527_030305_637811_6BD9E0C0 X-CRM114-Status: GOOD ( 20.15 ) 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 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