From: Steven Price <steven.price@arm•com>
To: Gavin Shan <gshan@redhat•com>,
kvm@vger•kernel.org, kvmarm@lists•linux.dev
Cc: Catalin Marinas <catalin.marinas@arm•com>,
Marc Zyngier <maz@kernel•org>, Will Deacon <will@kernel•org>,
James Morse <james.morse@arm•com>,
Oliver Upton <oliver.upton@linux•dev>,
Suzuki K Poulose <suzuki.poulose@arm•com>,
Zenghui Yu <yuzenghui@huawei•com>,
linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, Joey Gouly <joey.gouly@arm•com>,
Alexandru Elisei <alexandru.elisei@arm•com>,
Christoffer Dall <christoffer.dall@arm•com>,
Fuad Tabba <tabba@google•com>,
linux-coco@lists•linux.dev,
Ganapatrao Kulkarni <gankulkarni@os•amperecomputing.com>,
Shanker Donthineni <sdonthineni@nvidia•com>,
Alper Gun <alpergun@google•com>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel•org>,
Emi Kisanuki <fj0570is@fujitsu•com>,
Vishal Annapurve <vannapurve@google•com>,
WeiLin.Chang@arm•com, Lorenzo.Pieralisi2@arm•com
Subject: Re: [PATCH v14 06/44] arm64: RMI: Check for RMI support at init
Date: Wed, 3 Jun 2026 11:57:12 +0100 [thread overview]
Message-ID: <f0eddd9f-dbaa-48e9-888d-2e3514395c91@arm.com> (raw)
In-Reply-To: <3a0f6277-2b68-45db-a07f-16a177b0586d@redhat.com>
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 <steven.price@arm•com>
>>>> ---
>>>> 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 <linux/memblock.h>
>>>> +
>>>> +#include <asm/rmi_cmds.h>
>>>> +
>>>> +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
>
next prev parent reply other threads:[~2026-06-03 10:57 UTC|newest]
Thread overview: 125+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-13 13:17 [PATCH v14 00/44] arm64: Support for Arm CCA in KVM Steven Price
2026-05-13 13:17 ` [PATCH v14 01/44] kvm: arm64: Include kvm_emulate.h in kvm/arm_psci.h Steven Price
2026-05-21 10:19 ` Marc Zyngier
2026-05-21 15:11 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 02/44] kvm: arm64: Avoid including linux/kvm_host.h in kvm_pgtable.h Steven Price
2026-05-21 10:26 ` Marc Zyngier
2026-05-21 15:11 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 03/44] arm64: RME: Handle Granule Protection Faults (GPFs) Steven Price
2026-05-21 12:25 ` Marc Zyngier
2026-05-21 15:15 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 04/44] arm64: RMI: Add SMC definitions for calling the RMM Steven Price
2026-05-18 7:08 ` Gavin Shan
2026-05-20 16:01 ` Steven Price
2026-05-21 12:40 ` Marc Zyngier
2026-05-21 14:50 ` Suzuki K Poulose
2026-05-21 15:33 ` Steven Price
2026-05-22 9:58 ` Marc Zyngier
2026-06-03 10:15 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 05/44] arm64: RMI: Add wrappers for RMI calls Steven Price
2026-05-19 5:35 ` Aneesh Kumar K.V
2026-05-21 15:44 ` Steven Price
2026-05-21 0:21 ` Gavin Shan
2026-05-21 15:44 ` Steven Price
2026-05-21 12:49 ` Marc Zyngier
2026-05-21 15:44 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 06/44] arm64: RMI: Check for RMI support at init Steven Price
2026-05-21 0:39 ` Gavin Shan
2026-05-21 15:49 ` Steven Price
2026-05-25 6:58 ` Gavin Shan
2026-06-03 10:57 ` Steven Price [this message]
2026-05-21 13:02 ` Marc Zyngier
2026-06-03 10:57 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 07/44] arm64: RMI: Configure the RMM with the host's page size Steven Price
2026-05-21 0:51 ` Gavin Shan
2026-05-21 22:36 ` Suzuki K Poulose
2026-05-21 13:30 ` Marc Zyngier
2026-05-21 14:53 ` Suzuki K Poulose
2026-06-03 15:48 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 08/44] arm64: RMI: Ensure that the RMM has GPT entries for memory Steven Price
2026-05-19 5:55 ` Aneesh Kumar K.V
2026-06-03 15:48 ` Steven Price
2026-05-21 0:58 ` Gavin Shan
2026-06-03 15:48 ` Steven Price
2026-05-21 13:47 ` Marc Zyngier
2026-05-21 14:24 ` Marc Zyngier
2026-05-21 15:39 ` Suzuki K Poulose
2026-06-03 15:48 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 09/44] arm64: RMI: Provide functions to delegate/undelegate ranges of memory Steven Price
2026-05-21 13:59 ` Marc Zyngier
2026-05-21 16:01 ` Suzuki K Poulose
2026-05-22 10:02 ` Marc Zyngier
2026-06-04 14:43 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 10/44] arm64: RMI: Add support for SRO Steven Price
2026-05-14 8:01 ` Aneesh Kumar K.V
2026-05-14 9:33 ` Steven Price
2026-05-19 6:02 ` Aneesh Kumar K.V
2026-06-04 15:19 ` Steven Price
2026-05-21 4:38 ` Gavin Shan
2026-06-04 15:19 ` Steven Price
2026-05-21 14:35 ` Marc Zyngier
2026-06-04 15:19 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 11/44] arm64: RMI: Check for RMI support at KVM init Steven Price
2026-05-13 13:17 ` [PATCH v14 12/44] arm64: RMI: Check for LPA2 support Steven Price
2026-05-13 13:17 ` [PATCH v14 13/44] arm64: RMI: Define the user ABI Steven Price
2026-05-26 22:17 ` Wei-Lin Chang
2026-06-04 15:27 ` Steven Price
2026-05-27 15:21 ` Marc Zyngier
2026-06-02 11:15 ` Suzuki K Poulose
2026-06-04 15:27 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 14/44] arm64: RMI: Basic infrastructure for creating a realm Steven Price
2026-05-19 6:31 ` Aneesh Kumar K.V
2026-05-28 7:10 ` Marc Zyngier
2026-06-02 14:49 ` Suzuki K Poulose
2026-06-04 15:55 ` Steven Price
2026-05-13 13:17 ` [PATCH v14 15/44] kvm: arm64: Don't expose unsupported capabilities for realm guests Steven Price
2026-05-13 13:17 ` [PATCH v14 16/44] KVM: arm64: Allow passing machine type in KVM creation Steven Price
2026-05-13 13:17 ` [PATCH v14 17/44] arm64: RMI: RTT tear down Steven Price
2026-05-19 6:54 ` Aneesh Kumar K.V
2026-05-26 22:27 ` Wei-Lin Chang
2026-05-26 22:32 ` Wei-Lin Chang
2026-05-13 13:17 ` [PATCH v14 18/44] arm64: RMI: Activate realm on first VCPU run Steven Price
2026-05-13 13:17 ` [PATCH v14 19/44] arm64: RMI: Allocate/free RECs to match vCPUs Steven Price
2026-05-26 22:39 ` Wei-Lin Chang
2026-05-13 13:17 ` [PATCH v14 20/44] arm64: RMI: Support for the VGIC in realms Steven Price
2026-05-28 4:07 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 21/44] KVM: arm64: Support timers in realm RECs Steven Price
2026-05-28 4:11 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 22/44] arm64: RMI: Handle realm enter/exit Steven Price
2026-05-28 4:38 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 23/44] arm64: RMI: Handle RMI_EXIT_RIPAS_CHANGE Steven Price
2026-05-19 9:40 ` Aneesh Kumar K.V
2026-05-27 10:52 ` Wei-Lin Chang
2026-05-13 13:17 ` [PATCH v14 24/44] KVM: arm64: Handle realm MMIO emulation Steven Price
2026-05-28 5:03 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 25/44] KVM: arm64: Expose support for private memory Steven Price
2026-05-13 13:17 ` [PATCH v14 26/44] arm64: RMI: Allow populating initial contents Steven Price
2026-05-28 5:30 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 27/44] arm64: RMI: Set RIPAS of initial memslots Steven Price
2026-05-19 10:02 ` Aneesh Kumar K.V
2026-05-19 10:13 ` Suzuki K Poulose
2026-05-19 12:55 ` Aneesh Kumar K.V
2026-05-19 13:06 ` Suzuki K Poulose
2026-05-13 13:17 ` [PATCH v14 28/44] arm64: RMI: Create the realm descriptor Steven Price
2026-05-26 22:47 ` Wei-Lin Chang
2026-05-28 5:51 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 29/44] arm64: RMI: Runtime faulting of memory Steven Price
2026-06-05 6:23 ` Gavin Shan
2026-06-05 7:28 ` Lorenzo Pieralisi
2026-05-13 13:17 ` [PATCH v14 30/44] KVM: arm64: Handle realm VCPU load Steven Price
2026-05-13 13:17 ` [PATCH v14 31/44] KVM: arm64: Validate register access for a Realm VM Steven Price
2026-05-13 13:17 ` [PATCH v14 32/44] KVM: arm64: Handle Realm PSCI requests Steven Price
2026-05-28 6:55 ` Gavin Shan
2026-05-13 13:17 ` [PATCH v14 33/44] KVM: arm64: WARN on injected undef exceptions Steven Price
2026-05-13 13:17 ` [PATCH v14 34/44] arm64: RMI: allow userspace to inject aborts Steven Price
2026-05-13 13:17 ` [PATCH v14 35/44] arm64: RMI: support RSI_HOST_CALL Steven Price
2026-05-13 13:17 ` [PATCH v14 36/44] arm64: RMI: Allow checking SVE on VM instance Steven Price
2026-05-13 13:17 ` [PATCH v14 37/44] arm64: RMI: Prevent Device mappings for Realms Steven Price
2026-05-19 10:25 ` Aneesh Kumar K.V
2026-05-13 13:17 ` [PATCH v14 38/44] arm64: RMI: Propagate number of breakpoints and watchpoints to userspace Steven Price
2026-05-13 13:17 ` [PATCH v14 39/44] arm64: RMI: Set breakpoint parameters through SET_ONE_REG Steven Price
2026-05-13 13:17 ` [PATCH v14 40/44] arm64: RMI: Propagate max SVE vector length from RMM Steven Price
2026-05-13 13:17 ` [PATCH v14 41/44] arm64: RMI: Configure max SVE vector length for a Realm Steven Price
2026-05-13 13:17 ` [PATCH v14 42/44] arm64: RMI: Provide register list for unfinalized RMI RECs Steven Price
2026-05-13 13:17 ` [PATCH v14 43/44] arm64: RMI: Provide accurate register list Steven Price
2026-05-13 13:17 ` [PATCH v14 44/44] arm64: RMI: Enable realms to be created Steven Price
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