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 B124943E48B; Wed, 3 Jun 2026 10:57:20 +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=1780484244; cv=none; b=cr4+prq1nIfNxttRPH63898glaqsEC7OVjBA4puLdq/6p9RY8R3eAW4WaPW02Gq46+jQqQj9ZxkDT5TIo8PY4lA6jmNFWUQ19oSYXA5pI5XRjim4pokcZwBou+33V4zZFWlGiJm1SZv61a2y+wkWBtnmPmVp55yQ1XBnIn99SHk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780484244; c=relaxed/simple; bh=SAgpyeJ2aeueZn4wrvVe1OZsJjrJkzgdYaZDrIyIPiU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UG14X9piEBsnJbedIAh4g89YdtLCwJeB0EvCrkxfAgR6nCf5SbZOpD7yAVcSYckQLRxLENw8eKY85QBibgVWHyQh25KzYUTVBGCkpyy9SHM1bWmY8uk2AzZ7GT6NnEaj1bwMidZDqJZuC3ltjcSEixCH78zA2tmiOhOMEFF1PRQ= 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=tqUpSENx; 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="tqUpSENx" 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 E7B2032E4; Wed, 3 Jun 2026 03:57:14 -0700 (PDT) Received: from [10.57.26.22] (unknown [10.57.26.22]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A6CEB3F632; Wed, 3 Jun 2026 03:57:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1780484239; bh=SAgpyeJ2aeueZn4wrvVe1OZsJjrJkzgdYaZDrIyIPiU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=tqUpSENxeG0SKPwM2auSsdNR2MnbvVMsbBf17PLfnomuvP4sTFKKqtAj/CEsvGOgJ RfzZMYa11Jh1JViWeQcUAS6TO/OdzQuGZzkwU020GsIj0LDzT+2r8LI/OERjrwrLXK ySyuIUrwj2dYafSreRlXmz2QaMx+cMthgy/asKsY= Message-ID: Date: Wed, 3 Jun 2026 11:57:12 +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> <78425c0d-86c5-457f-b171-a4c8dd3acb7d@arm.com> <3a0f6277-2b68-45db-a07f-16a177b0586d@redhat.com> From: Steven Price Content-Language: en-GB In-Reply-To: <3a0f6277-2b68-45db-a07f-16a177b0586d@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 25/05/2026 07:58, Gavin Shan wrote: > Hi Steve, > > On 5/22/26 1:49 AM, Steven Price wrote: >> On 21/05/2026 01:39, Gavin Shan wrote: >>> 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. >> > > I think the return value would be consistent to the value of > 'arm64_rmi_is_available'. > 'arm64_rmi_is_available' is true when zero is returned, otherwise, > 'arm64_rmi_is_available' > is false. > > With the consistency between the return value and > 'arm64_rmi_is_available', users are > able to know the value of 'arm64_rmi_is_available' through kernel > parameter 'initcall_debug'. > With the kernel parameter, the initcalls including arm64_init_rmi() are > traced and its > return value is outputted in the traced messages, seeing > do_trace_initcall_start(). Fair enough, and actually refactoring this function to pass error codes up the call stack I think does improve the look. Thanks, Steve >> 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 >