From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 48B68365A0B; Thu, 21 May 2026 15:50:04 +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=1779378605; cv=none; b=XtNre9IDKFms8dif70AISRpafPUctdpHpruKrYjB48Yy4Y0qEH/1HtNp/YMQZXdzuri2JuRId3G27gfd/oOOAzVhiBWrAUYEtkz8olSSs8NGf3abLKp9tjQNY1r/sRDE423/wHMRzRSvfcL+ejyYug+JKFZ0bt/7qAHNFRKkI+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779378605; c=relaxed/simple; bh=mMghuHi21M3rXnjm/M0jpANdblyW2ZAdsbpFbgKLRXI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=WkYo+qIjzl1XPhr3v8WD1glt9YBCQNThrzRRoRGbRJ+RRjN6Z4jRJFlwMs6NVzRMw1bNq1A4mUDd83AUZ9YoqCDz8Lfgi5KnJR8EK4NE+ZrJXh/1Fmsj/4y3upZlrDIadzH4OA1SHSS7KqWC28K6JQWOYus7phP7J09wR2vEHPg= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=vTa59URD; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="vTa59URD" 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 8129F1C25; Thu, 21 May 2026 08:49:58 -0700 (PDT) Received: from [10.1.32.22] (e122027.cambridge.arm.com [10.1.32.22]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E8AF03F632; Thu, 21 May 2026 08:49:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1779378603; bh=mMghuHi21M3rXnjm/M0jpANdblyW2ZAdsbpFbgKLRXI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=vTa59URD+6XdILapZywItbSczRW9VRRCTd016APcjuY/07ZdrQgHihhQStO6DB2Rw /aK6pONHDoWdWA9mM7r4FFOPwSpTjPPRniW7rVoko3lFJGYMMQDk6Jml1wvMGql3Py KMsfk8ppzYIRmjyaauqu3vl0H8+W/ZWG+njYFoCs= Message-ID: <78425c0d-86c5-457f-b171-a4c8dd3acb7d@arm.com> Date: Thu, 21 May 2026 16:49:56 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 06/44] arm64: RMI: Check for RMI support at init To: Gavin Shan , kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: 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 , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo.Pieralisi2@arm.com References: <20260513131757.116630-1-steven.price@arm.com> <20260513131757.116630-7-steven.price@arm.com> From: Steven Price Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 21/05/2026 01:39, Gavin Shan wrote: > Hi Steven, > > On 5/13/26 11:17 PM, Steven Price wrote: >> Query the RMI version number and check if it is a compatible version. >> The first two feature registers are read and exposed for future code to >> use. >> >> Signed-off-by: Steven Price >> --- >> v14: >>   * This moves the basic RMI setup into the 'kernel' directory. This is >>     because RMI will be used for some features outside of KVM so should >>     be available even if KVM isn't compiled in. >> --- >>   arch/arm64/include/asm/rmi_cmds.h |  3 ++ >>   arch/arm64/kernel/Makefile        |  2 +- >>   arch/arm64/kernel/cpufeature.c    |  1 + >>   arch/arm64/kernel/rmi.c           | 65 +++++++++++++++++++++++++++++++ >>   4 files changed, 70 insertions(+), 1 deletion(-) >>   create mode 100644 arch/arm64/kernel/rmi.c >> > > [...] > >> diff --git a/arch/arm64/kernel/rmi.c b/arch/arm64/kernel/rmi.c >> new file mode 100644 >> index 000000000000..99c1ccc35c11 >> --- /dev/null >> +++ b/arch/arm64/kernel/rmi.c >> @@ -0,0 +1,65 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * Copyright (C) 2023-2025 ARM Ltd. >> + */ >> + >> +#include >> + >> +#include >> + >> +unsigned long rmm_feat_reg0; >> +unsigned long rmm_feat_reg1; >> + >> +static int rmi_check_version(void) >> +{ >> +    struct arm_smccc_res res; >> +    unsigned short version_major, version_minor; >> +    unsigned long host_version = RMI_ABI_VERSION(RMI_ABI_MAJOR_VERSION, >> +                             RMI_ABI_MINOR_VERSION); >> +    unsigned long aa64pfr0 = >> read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1); >> + >> +    /* If RME isn't supported, then RMI can't be */ >> +    if (cpuid_feature_extract_unsigned_field(aa64pfr0, >> ID_AA64PFR0_EL1_RME_SHIFT) == 0) >> +        return -ENXIO; >> + >> +    arm_smccc_1_1_invoke(SMC_RMI_VERSION, host_version, &res); >> + >> +    if (res.a0 == SMCCC_RET_NOT_SUPPORTED) >> +        return -ENXIO; >> + >> +    version_major = RMI_ABI_VERSION_GET_MAJOR(res.a1); >> +    version_minor = RMI_ABI_VERSION_GET_MINOR(res.a1); >> + >> +    if (res.a0 != RMI_SUCCESS) { >> +        unsigned short high_version_major, high_version_minor; >> + >> +        high_version_major = RMI_ABI_VERSION_GET_MAJOR(res.a2); >> +        high_version_minor = RMI_ABI_VERSION_GET_MINOR(res.a2); >> + >> +        pr_err("Unsupported RMI ABI (v%d.%d - v%d.%d) we want v%d.%d\n", >> +               version_major, version_minor, >> +               high_version_major, high_version_minor, >> +               RMI_ABI_MAJOR_VERSION, >> +               RMI_ABI_MINOR_VERSION); >> +        return -ENXIO; >> +    } >> + >> +    pr_info("RMI ABI version %d.%d\n", version_major, version_minor); >> + >> +    return 0; >> +} >> + >> +static int __init arm64_init_rmi(void) >> +{ >> +    /* Continue without realm support if we can't agree on a version */ >> +    if (rmi_check_version()) >> +        return 0; > > Is this still a valid point that we have to return zero on errors returned > from rmi_check_version() or other other function calls like rmi_features()? > arm64_init_rmi() is triggered by subsys_initcall() where the return value > needs to indicate success or failure. It's fine to return error code from > arm64_init_rmi() in the path. Hmm, I guess now this is moved to arm64 code this indeed doesn't need to. Within a module I believe an error return can fail the module loading. I'm not sure it really makes much difference though - if this initialisation fails then it's not really an error - it just means the feature is unavailable. Thanks, Steve >> + >> +    if (WARN_ON(rmi_features(0, &rmm_feat_reg0))) >> +        return 0; >> +    if (WARN_ON(rmi_features(1, &rmm_feat_reg1))) >> +        return 0; >> + >> +    return 0; >> +} >> +subsys_initcall(arm64_init_rmi); > > Thanks, > Gavin >