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 8E0F8CD5BAC for ; Thu, 21 May 2026 15:50:14 +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: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=5DkSM4AdV+H8uwN5nTs766MuYJZjikfQqQCWWJARhxk=; b=OuKVYsCfldAkR+fQHnQGIV5p63 4zGkRSQ/6boN2q7hh6emtm5TqLZNWxTU/Umm2mifdP3UZneHIoHEuWrKMrCScXB9+LYz69fp4vr/t TXqGjW5QPdsoAE2fmUTutTUzGieVKjAGuTinLKlGjfkWebD1MSnVl2Q+cwOPrEHtS6sWtcWeULWx+ gVHu9PZYEQQt2JJj4iu4EfnBFRCgqkkEuJYXZ1JhxaAqIByfseVlXJuNP3kjAcROZUjvHQroyxjB4 XjyHOeRcx4/HqsFLHkzoAIMLa7RZCqB5Rs73iopmULPMgQyYBOpz9dILqH+tGwGyd/v/KaT1G7SV2 0WAsVgow==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQ5ey-00000008OsN-1OpD; Thu, 21 May 2026 15:50:08 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQ5ev-00000008Orf-3Bl7 for linux-arm-kernel@lists.infradead.org; Thu, 21 May 2026 15:50:07 +0000 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 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260521_085005_875562_3E879BA9 X-CRM114-Status: GOOD ( 26.22 ) 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 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 >