linux-kernel - Re: [RFC PATCH 04/28] arm64: RME: Check for RME support at KVM init

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Date: Mon, 18 Mar 2024 11:22:41 +0000
From: Steven Price <steven.price@....com>
To: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 kvm@...r.kernel.org, kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>,
 Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu
 <yuzenghui@...wei.com>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Joey Gouly <joey.gouly@....com>,
 Alexandru Elisei <alexandru.elisei@....com>,
 Christoffer Dall <christoffer.dall@....com>, Fuad Tabba <tabba@...gle.com>,
 linux-coco@...ts.linux.dev
Subject: Re: [RFC PATCH 04/28] arm64: RME: Check for RME support at KVM init

On 18/03/2024 07:17, Ganapatrao Kulkarni wrote:
> 
> 
> On 27-01-2023 04:59 pm, Steven Price wrote:
>> Query the RMI version number and check if it is a compatible version. A
>> static key is also provided to signal that a supported RMM is available.
>>
>> Functions are provided to query if a VM or VCPU is a realm (or rec)
>> which currently will always return false.
>>
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>>   arch/arm64/include/asm/kvm_emulate.h | 17 ++++++++++
>>   arch/arm64/include/asm/kvm_host.h    |  4 +++
>>   arch/arm64/include/asm/kvm_rme.h     | 22 +++++++++++++
>>   arch/arm64/include/asm/virt.h        |  1 +
>>   arch/arm64/kvm/Makefile              |  3 +-
>>   arch/arm64/kvm/arm.c                 |  8 +++++
>>   arch/arm64/kvm/rme.c                 | 49 ++++++++++++++++++++++++++++
>>   7 files changed, 103 insertions(+), 1 deletion(-)
>>   create mode 100644 arch/arm64/include/asm/kvm_rme.h
>>   create mode 100644 arch/arm64/kvm/rme.c
>>

[...]

>> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
>> new file mode 100644
>> index 000000000000..f6b587bc116e
>> --- /dev/null
>> +++ b/arch/arm64/kvm/rme.c
>> @@ -0,0 +1,49 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2023 ARM Ltd.
>> + */
>> +
>> +#include <linux/kvm_host.h>
>> +
>> +#include <asm/rmi_cmds.h>
>> +#include <asm/virt.h>
>> +
>> +static int rmi_check_version(void)
>> +{
>> +    struct arm_smccc_res res;
>> +    int version_major, version_minor;
>> +
>> +    arm_smccc_1_1_invoke(SMC_RMI_VERSION, &res);
>> +
>> +    if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
>> +        return -ENXIO;
>> +
>> +    version_major = RMI_ABI_VERSION_GET_MAJOR(res.a0);
>> +    version_minor = RMI_ABI_VERSION_GET_MINOR(res.a0);
>> +
>> +    if (version_major != RMI_ABI_MAJOR_VERSION) {
>> +        kvm_err("Unsupported RMI ABI (version %d.%d) we support %d\n",
> 
> Can we please replace "we support" to host supports.
> Also in the patch present in the repo, you are using variable
> our_version, can this be changed to host_version?

Sure, I do have a bad habit using "we" - thanks for point it out.

Steve

>> +            version_major, version_minor,
>> +            RMI_ABI_MAJOR_VERSION);
>> +        return -ENXIO;
>> +    }
>> +
>> +    kvm_info("RMI ABI version %d.%d\n", version_major, version_minor);
>> +
>> +    return 0;
>> +}
>> +
>> +int kvm_init_rme(void)
>> +{
>> +    if (PAGE_SIZE != SZ_4K)
>> +        /* Only 4k page size on the host is supported */
>> +        return 0;
>> +
>> +    if (rmi_check_version())
>> +        /* Continue without realm support */
>> +        return 0;
>> +
>> +    /* Future patch will enable static branch kvm_rme_is_available */
>> +
>> +    return 0;
>> +}
> 
> Thanks,
> Ganapat