linux-kernel - Re: [PATCH v3 1/1] arm64: rsi: Add automatic arm-cca-guest module loading

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Message-ID: <8ef0a63c-bde2-443b-b2fd-59d24c5e18e6@arm.com>
Date: Tue, 17 Dec 2024 14:16:59 -0600
From: Jeremy Linton <jeremy.linton@....com>
To: Itaru Kitayama <itaru.kitayama@...ux.dev>
Cc: linux-arm-kernel@...ts.infradead.org, suzuki.poulose@....com,
 gshan@...hat.com, steven.price@....com, sami.mujawar@....com,
 catalin.marinas@....com, will@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] arm64: rsi: Add automatic arm-cca-guest module
 loading

Hi,

On 12/7/24 10:38 PM, Itaru Kitayama wrote:
> Hi Jeremy,
> 
> On Fri, Dec 06, 2024 at 07:21:28PM -0600, Jeremy Linton wrote:
>> The TSM module provides guest identification and attestation when a
>> guest runs in CCA mode. By creating a dummy platform device, let's
> 
> Perhaps could you spell out like; a guest runs in the Realm state?

Thanks for looking at this.

I thought that was evident from the rest of the commits here, but sure.

Thanks again.


> 
> Thanks,
> Itaru.
>   
>> ensure the module is automatically loaded. The udev daemon loads the
>> TSM module after it receives a device addition event. Once that
>> happens, it can be used earlier in the boot process to decrypt the
>> rootfs.
>>
>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>> Reviewed-by: Gavin Shan <gshan@...hat.com>
>> ---
>>   arch/arm64/include/asm/rsi.h                    |  2 ++
>>   arch/arm64/kernel/rsi.c                         | 15 +++++++++++++++
>>   drivers/virt/coco/arm-cca-guest/arm-cca-guest.c |  8 ++++++++
>>   3 files changed, 25 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/rsi.h b/arch/arm64/include/asm/rsi.h
>> index 188cbb9b23f5..b42aeac05340 100644
>> --- a/arch/arm64/include/asm/rsi.h
>> +++ b/arch/arm64/include/asm/rsi.h
>> @@ -10,6 +10,8 @@
>>   #include <linux/jump_label.h>
>>   #include <asm/rsi_cmds.h>
>>   
>> +#define RSI_PDEV_NAME "arm-cca-dev"
>> +
>>   DECLARE_STATIC_KEY_FALSE(rsi_present);
>>   
>>   void __init arm64_rsi_init(void);
>> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
>> index 3031f25c32ef..5434e5496ac2 100644
>> --- a/arch/arm64/kernel/rsi.c
>> +++ b/arch/arm64/kernel/rsi.c
>> @@ -8,6 +8,7 @@
>>   #include <linux/psci.h>
>>   #include <linux/swiotlb.h>
>>   #include <linux/cc_platform.h>
>> +#include <linux/platform_device.h>
>>   
>>   #include <asm/io.h>
>>   #include <asm/mem_encrypt.h>
>> @@ -140,3 +141,17 @@ void __init arm64_rsi_init(void)
>>   	static_branch_enable(&rsi_present);
>>   }
>>   
>> +static struct platform_device rsi_dev = {
>> +	.name = RSI_PDEV_NAME,
>> +	.id = PLATFORM_DEVID_NONE
>> +};
>> +
>> +static int __init rsi_init(void)
>> +{
>> +	if (is_realm_world() &&
>> +	    platform_device_register(&rsi_dev))
>> +		pr_err("failed to register rsi platform device\n");
>> +	return 0;
>> +}
>> +
>> +arch_initcall(rsi_init)
>> diff --git a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c b/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
>> index 488153879ec9..87f162736b2e 100644
>> --- a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
>> +++ b/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
>> @@ -6,6 +6,7 @@
>>   #include <linux/arm-smccc.h>
>>   #include <linux/cc_platform.h>
>>   #include <linux/kernel.h>
>> +#include <linux/mod_devicetable.h>
>>   #include <linux/module.h>
>>   #include <linux/smp.h>
>>   #include <linux/tsm.h>
>> @@ -219,6 +220,13 @@ static void __exit arm_cca_guest_exit(void)
>>   }
>>   module_exit(arm_cca_guest_exit);
>>   
>> +/* modalias, so userspace can autoload this module when RSI is available */
>> +static const struct platform_device_id arm_cca_match[] __maybe_unused = {
>> +	{ RSI_PDEV_NAME, 0},
>> +	{ }
>> +};
>> +
>> +MODULE_DEVICE_TABLE(platform, arm_cca_match);
>>   MODULE_AUTHOR("Sami Mujawar <sami.mujawar@....com>");
>>   MODULE_DESCRIPTION("Arm CCA Guest TSM Driver");
>>   MODULE_LICENSE("GPL");
>> -- 
>> 2.46.0
>>