linux-kernel - Re: [PATCH v4 07/43] arm64: RME: Check for RME support at KVM init

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Message-ID: <8e17105a-8732-46df-8f3e-01a168558231@redhat.com>
Date: Thu, 12 Sep 2024 18:49:38 +1000
From: Gavin Shan <gshan@...hat.com>
To: Steven Price <steven.price@....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,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Alper Gun <alpergun@...gle.com>
Subject: Re: [PATCH v4 07/43] arm64: RME: Check for RME support at KVM init

On 8/22/24 1:38 AM, 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>
> ---
> Changes since v2:
>   * Drop return value from kvm_init_rme(), it was always 0.
>   * Rely on the RMM return value to identify whether the RSI ABI is
>     compatible.
> ---
>   arch/arm64/include/asm/kvm_emulate.h | 17 +++++++++
>   arch/arm64/include/asm/kvm_host.h    |  4 ++
>   arch/arm64/include/asm/kvm_rme.h     | 56 ++++++++++++++++++++++++++++
>   arch/arm64/include/asm/virt.h        |  1 +
>   arch/arm64/kvm/Makefile              |  3 +-
>   arch/arm64/kvm/arm.c                 |  6 +++
>   arch/arm64/kvm/rme.c                 | 50 +++++++++++++++++++++++++
>   7 files changed, 136 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..418685fbf6ed
> --- /dev/null
> +++ b/arch/arm64/kvm/rme.c
> @@ -0,0 +1,50 @@
> +// 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;
> +	unsigned long host_version = RMI_ABI_VERSION(RMI_ABI_MAJOR_VERSION,
> +						     RMI_ABI_MINOR_VERSION);
> +
> +	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) {
> +		kvm_err("Unsupported RMI ABI (v%d.%d) host supports v%d.%d\n",
> +			version_major, version_minor,
> +			RMI_ABI_MAJOR_VERSION,
> +			RMI_ABI_MINOR_VERSION);

This message is perhaps something like below since a range of versions can be
supported by one particular RMM release.

     kvm_err("Unsupported RMI ABI v%d.%d. Host supports v%ld.%ld - v%ld.%ld\n",
             RMI_ABI_MAJOR_VERSION, RMI_ABI_MINOR_VERSION,
             RMI_ABI_VERSION_GET_MAJOR(res.a1), RMI_ABI_VERSION_GET_MINOR(res.a1),
             RMI_ABI_VERSION_GET_MAJOR(res.a2), RMI_ABI_VERSION_GET_MINOR(res.a2));

> +		return -ENXIO;
> +	}
> +
> +	kvm_info("RMI ABI version %d.%d\n", version_major, version_minor);
> +

We probably need to print the requested version, instead of the lower implemented
version, if I'm correct. At present, both of them have been fixed to v1.0 and we
don't have a problem though.

         kvm_info("RMI ABI version v%d.%d\n", RMI_ABI_MAJOR_VERSION, RMI_ABI_MINOR_VERSION);

> +	return 0;
> +}
> +

Thanks,
Gavin