linux-kernel - Re: [PATCH] coco: guest: arm64: Update ARM CCA guest driver

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Message-ID: <20251009112529.00001b41@huawei.com>
Date: Thu, 9 Oct 2025 11:25:29 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
CC: <linux-coco@...ts.linux.dev>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Steven Price <steven.price@....com>, "Gavin
 Shan" <gshan@...hat.com>, Suzuki K Poulose <suzuki.poulose@....com>, "Jeremy
 Linton" <jeremy.linton@....com>, Sami Mujawar <sami.mujawar@....com>
Subject: Re: [PATCH] coco: guest: arm64: Update ARM CCA guest driver

On Wed,  8 Oct 2025 18:57:58 +0530
"Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org> wrote:

> Make preparatory updates to the ARM CCA guest driver:
> 
>  - Switch from using a platform device to a faux device (based on
>    feedback in [1])
>  - Rename the device from `arm-cca-dev` to `arm-rsi-dev`, so that the
>    host driver can register an equivalent `arm-rmi-dev`
> 
> These changes are purely structural and introduce no new functionality.
> Subsequent patches will extend this driver to add guest device
> assignment support.
> 
> [1] https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh
> 

Slight preference for:
Link: https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh #1
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@...nel.org>
> ---
> NOTE:
> This patch is sent early outside the patchseries to avoid userspace from
> depending on the presence of the newly introduced platform device.
> The platform device was added in v6.14-rc1. 
> 

A few trivial things inline. With those in mind.
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>

> diff --git a/drivers/virt/coco/arm-cca-guest/Makefile b/drivers/virt/coco/arm-cca-guest/Makefile
> index 69eeba08e98a..609462ea9438 100644
> --- a/drivers/virt/coco/arm-cca-guest/Makefile
> +++ b/drivers/virt/coco/arm-cca-guest/Makefile
> @@ -1,2 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0-only
> +#

Unrelated change. I'd drop it.

>  obj-$(CONFIG_ARM_CCA_GUEST) += arm-cca-guest.o
> +
> +arm-cca-guest-$(CONFIG_TSM) +=  arm-cca.o

extra space after = seems a bit odd.

> diff --git a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c b/drivers/virt/coco/arm-cca-guest/arm-cca.c
> similarity index 85%
> rename from drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
> rename to drivers/virt/coco/arm-cca-guest/arm-cca.c
> index 0c9ea24a200c..89d9e7f8eb5d 100644
> --- a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
> +++ b/drivers/virt/coco/arm-cca-guest/arm-cca.c
> @@ -1,8 +1,9 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  /*
> - * Copyright (C) 2023 ARM Ltd.
> + * Copyright (C) 2025 ARM Ltd.

I'd expect a date range rather than updating copyright for whole file
like this. The untouched bit will still be 2023 era code.

>   */

> +static int cca_tsm_probe(struct faux_device *fdev)
>  {
>  	int ret;
>  
>  	if (!is_realm_world())
>  		return -ENODEV;
>  
> -	ret = tsm_report_register(&arm_cca_tsm_ops, NULL);
> -	if (ret < 0)
> +	ret = tsm_report_register(&arm_cca_tsm_report_ops, NULL);
> +	if (ret < 0) {
>  		pr_err("Error %d registering with TSM\n", ret);
> +		return ret;
> +	}
> +
> +	ret = devm_add_action_or_reset(&fdev->dev, unregister_cca_tsm_report, NULL);
> +	if (ret < 0) {
> +		pr_err("Error %d registering devm action\n", ret);

I believe (not checked today) that devm_add_action_or_reset() can only fail
with -ENOMEM due to an allocation failure and we generally don't print
extra error messages if that happens.
So I would drop this pr_err.

> +		unregister_cca_tsm_report(NULL);
> +		return ret;
> +	}
>  
>  	return ret;
>  }