linux-kernel - Re: [PATCH v2 13/14] arm64: rsi: Interfaces to query attestation token

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Date: Fri, 31 May 2024 17:29:24 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Steven Price <steven.price@....com>,
 Catalin Marinas <catalin.marinas@....com>
Cc: kvm@...r.kernel.org, kvmarm@...ts.linux.dev,
 Sami Mujawar <sami.mujawar@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, 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>
Subject: Re: [PATCH v2 13/14] arm64: rsi: Interfaces to query attestation
 token

On 22/05/2024 16:52, Steven Price wrote:
> On 15/05/2024 12:10, Catalin Marinas wrote:
>> On Fri, Apr 12, 2024 at 09:42:12AM +0100, Steven Price wrote:
>>> diff --git a/arch/arm64/include/asm/rsi_cmds.h b/arch/arm64/include/asm/rsi_cmds.h
>>> index b4cbeafa2f41..c1850aefe54e 100644
>>> --- a/arch/arm64/include/asm/rsi_cmds.h
>>> +++ b/arch/arm64/include/asm/rsi_cmds.h
>>> @@ -10,6 +10,9 @@
>>>   
>>>   #include <asm/rsi_smc.h>
>>>   
>>> +#define GRANULE_SHIFT		12
>>> +#define GRANULE_SIZE		(_AC(1, UL) << GRANULE_SHIFT)
>>
>> The name is too generic and it goes into a header file. Also maybe move
>> it to rsi.h, and use it for other definitions like rsi_config struct
>> size and alignment.
>>
> 
> The realm config structure although it 'happens to be' granule sized
> isn't really required to be - so I think it would be a bit confusing to
> specify that.

The struct realm_config must be aligned to GRANULE_SIZE and the argument
must be as such aligned.

> 
> There are only two other interfaces that require this:
>   * RSI_IPA_STATE_GET - completely unused so far
>   * RSI_ATTESTATION_TOKEN_CONTINUE - the buffer has to be contained with
>     a granule, so it affects the maximum length per operation.
> 
> I'll rename to RSI_GRANULE_{SHIFT,SIZE}, but I'm not sure it really

That looks good to me.

Suzuki


> belongs in rsi.h because none of that functionality cares about the
> granule size (indeed the driver in the following patch doesn't include
> rsi.h).
> 
> Thanks,
> Steve