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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ac5f280fecsm3307221a91.13.2026.10.14.00.26.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Oct 2026 00:26:23 -0700 (PDT) Message-ID: <3fbd4739-a4eb-4428-95ae-ead22e7cf9f2@redhat.com> Date: Wed, 14 Oct 2026 17:26:14 +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 v22 02/10] firmware: arm_rmm: Check for RMI support at init To: Suzuki K Poulose , kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: maz@kernel.org, will@kernel.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com, sudeep.holla@arm.com, jonathan.cameron@oss.qualcomm.com References: <20261002061507.1600269-1-suzuki.poulose@arm.com> <20261002061507.1600269-3-suzuki.poulose@arm.com> <2586e689-c27d-4e4c-8c69-03e24259cb96@redhat.com> <8be050e3-8af1-4f04-902f-9bc01b209dd0@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <8be050e3-8af1-4f04-902f-9bc01b209dd0@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/13/26 7:58 PM, Suzuki K Poulose wrote: > On 13/10/2026 04:53, Gavin Shan wrote: >> Hi Suzuki, >> >> On 10/2/26 4:14 PM, Suzuki K Poulose wrote: >>> From: Steven Price >>> >>> Query the RMI version number and check if it is a compatible version. >>> All RMM feature registers are read and exposed for future code to >>> use. Also restrict the support to SMC conduit. >>> >>> We only support this for Little Endian kernels, the Big Endian kernel >>> support is anyway marked BROKEN and is being removed. >>> >>> Cc: Marc Zyngier >>> Cc: Oliver Upton >>> Reviewed-by: Jonathan Cameron >>> Reviewed-by: Gavin Shan >>> Reviewed-by: Catalin Marinas >>> Tested-by: Gavin Shan >>> Signed-off-by: Steven Price >>> Co-developed-by: Suzuki K Poulose >>> Signed-off-by: Suzuki K Poulose >>> --- >> >> [...] >> >>> --- >>>   MAINTAINERS                       |   2 + >>>   arch/arm64/Kconfig                |   1 + >>>   arch/arm64/kernel/cpufeature.c    |   1 + >>>   arch/arm64/kvm/sys_regs.c         |   2 + >>>   drivers/firmware/Kconfig          |   1 + >>>   drivers/firmware/Makefile         |   1 + >>>   drivers/firmware/arm_rmm/Kconfig  |  25 +++++++ >>>   drivers/firmware/arm_rmm/Makefile |   1 + >>>   drivers/firmware/arm_rmm/rmi.c    | 112 ++++++++++++++++++++++++++++++ >>>   include/linux/arm-rmi-cmds.h      |  48 +++++++++++++ >>>   10 files changed, 194 insertions(+) >>>   create mode 100644 drivers/firmware/arm_rmm/Kconfig >>>   create mode 100644 drivers/firmware/arm_rmm/Makefile >>>   create mode 100644 drivers/firmware/arm_rmm/rmi.c >>>   create mode 100644 include/linux/arm-rmi-cmds.h >>> >> >> [...] >> >>> diff --git a/drivers/firmware/arm_rmm/rmi.c b/drivers/firmware/ arm_rmm/rmi.c >>> new file mode 100644 >>> index 0000000000000..06f5392c982d2 >>> --- /dev/null >>> +++ b/drivers/firmware/arm_rmm/rmi.c >>> @@ -0,0 +1,112 @@ >>> +// SPDX-License-Identifier: GPL-2.0 >>> +/* >>> + * Copyright (C) 2023-2026 ARM Ltd. >>> + */ >>> + >>> +#include >>> +#include >>> +#include >>> +#include >>> + >>> +#include >>> +#include >>> + >>> +/* RMM v2.0 defines RmiFeatureRegister0 to RmiFeatureRegister4. */ >>> +static unsigned long rmi_feat_reg_cache[5] __ro_after_init; >>> + >>> +static int rmi_check_version(void) >>> +{ >>> +    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); >>> +    struct arm_smccc_1_2_regs res = { >>> +        SMC_RMI_VERSION, host_version, >>> +    }; >>> + >>> +    /* 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; >>> + >>> +    if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_SMC) >>> +        return -ENXIO; >> >> I think we need to ensure SMCCC version is v1.2 or a newer one here? arm_smccc_1_2_smc() >> is immediately called by rmi_smccc_invoke() after this check. >> >>      if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_SMC || >>              arm_smccc_get_version() < ARM_SMCCC_VERSION_1_2) > > We could. But I am wondering if that adds any value ? If the RMM > exists and responds to the RMI_ABI_VERSION, it must be so on a > platform with v1.2 or greater ? The extra check doesn't hurt. > It's required as documented in section "B1.1 overview" of RMM-spec-v2.0-bet3. In the same section, there are more requirements regarding the SMCCC version when SVE/SME are supported. I don't see a practical problem if the check is missed since the combination of TF-A and TF-RMM are the only RMM-spec-v2.0-bet3 implementation (as I knew) where the SMCCC version has been set to v1.5 in the 'master' branch. Thanks, Gavin > Suzuki > >>          return -ENXIO; >> >> Thanks, >> Gavin >> >>> + >>> +    rmi_smccc_invoke(&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; >>> +} >>> + >> >> [...] >> >> >> >