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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-83f19663cfdsm27427984b3a.9.2026.05.20.17.39.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 May 2026 17:39:49 -0700 (PDT) Message-ID: Date: Thu, 21 May 2026 10:39:39 +1000 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: Steven Price , 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> Content-Language: en-US From: Gavin Shan In-Reply-To: <20260513131757.116630-7-steven.price@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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. > + > + 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