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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ac5f05083fsm4391258a91.1.2026.10.14.03.58.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Oct 2026 03:58:09 -0700 (PDT) Message-ID: <0ceda99f-0352-474b-a30a-c5e79b817c2d@redhat.com> Date: Wed, 14 Oct 2026 20:58:00 +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> <3fbd4739-a4eb-4428-95ae-ead22e7cf9f2@redhat.com> <799fb810-c33e-4d0e-9a70-7092c0a681ff@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <799fb810-c33e-4d0e-9a70-7092c0a681ff@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/14/26 7:19 PM, Suzuki K Poulose wrote: > On 14/10/2026 08:26, Gavin Shan wrote: >> 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. > > Reading the RMM spec again, DFNMZ lists how one can detect if the RMM > ABI is present. That specifies that the user checks for SMCCC > version >= 1.1, which we do by using arm_smccc_1_1_get_conduit(). > > Then checking the R{M,S}I_VERSION call is sufficient. So, I think > we are good here. Do you agree ? > arm_smccc_1_1_get_conduit() ensures SMCCC version >= v1.1, but we need SMCCC version >= v1.2. We will have problem if the firmware only supports SMCCC v1.1 and R{M,S}I_VERSION is coincidentally supported. In this rare (even impossible) case, it's not sufficient to check R{M,S}I_VERSION as I understand. As far as TF-A+TF-RMM is concerned, I agree there is no issue. However, the extra check doesn't hurt and make the code following the spec a bit more strictly? :-) Thanks, Gavin > Suzuki > >> >> 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; >>>>> +} >>>>> + >>>> >>>> [...] >>>> >>>> >>>> >>> >> >