linux-kernel - Re: [PATCH RESEND v2 03/12] coco: guest: arm64: Drop dummy RSI platform device stub

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Message-ID: <20251029165403.00000178@huawei.com>
Date: Wed, 29 Oct 2025 16:54:03 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
CC: <linux-coco@...ts.linux.dev>, <kvmarm@...ts.linux.dev>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<dan.j.williams@...el.com>, <aik@....com>, <lukas@...ner.de>, Samuel Ortiz
	<sameo@...osinc.com>, Xu Yilun <yilun.xu@...ux.intel.com>, Jason Gunthorpe
	<jgg@...pe.ca>, Suzuki K Poulose <Suzuki.Poulose@....com>, Steven Price
	<steven.price@....com>, Bjorn Helgaas <helgaas@...nel.org>, Catalin Marinas
	<catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>, Will Deacon
	<will@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>
Subject: Re: [PATCH RESEND v2 03/12] coco: guest: arm64: Drop dummy RSI
 platform device stub

On Mon, 27 Oct 2025 15:25:53 +0530
"Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org> wrote:

> The SMCCC firmware driver now creates the `arm-smccc` platform device
> and also creates the CCA auxiliary devices once the RSI ABI is
> discovered. This makes the arch-specific arm64_create_dummy_rsi_dev()
> helper redundant. Remove the arm-cca-dev platform device registration
> and let the SMCCC probe manage the RSI device.
> 
> systemd match on platform:arm-cca-dev for confidential vm detection [1].
> Losing the platform device registration can break that. Keeping this
> removal in its own change makes it easy to revert if that regression
> blocks the rollout.
> 
> [1] https://lore.kernel.org/all/4a7d84b2-2ec4-4773-a2d5-7b63d5c683cf@arm.com
> 
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@...nel.org>
Fair enough keeping it separate for now I guess.
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>

(and I see from that thread I did look at the RFC but clearly forgot all
 about it :( )
> ---
>  arch/arm64/kernel/rsi.c | 15 ---------------
>  1 file changed, 15 deletions(-)
> 
> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
> index 5d711942e543..1b716d18b80e 100644
> --- a/arch/arm64/kernel/rsi.c
> +++ b/arch/arm64/kernel/rsi.c
> @@ -158,18 +158,3 @@ void __init arm64_rsi_init(void)
>  
>  	static_branch_enable(&rsi_present);
>  }
> -
> -static struct platform_device rsi_dev = {
> -	.name = "arm-cca-dev",
> -	.id = PLATFORM_DEVID_NONE
> -};
> -
> -static int __init arm64_create_dummy_rsi_dev(void)
> -{
> -	if (is_realm_world() &&
> -	    platform_device_register(&rsi_dev))
> -		pr_err("failed to register rsi platform device\n");
> -	return 0;
> -}
> -
> -arch_initcall(arm64_create_dummy_rsi_dev)