linux-kernel - Re: [PATCH v7 05/45] arm64: RME: Add wrappers for RMI calls

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Message-ID: <1e1aa766-c358-4a4f-918e-f0044fe499fe@redhat.com>
Date: Wed, 5 Mar 2025 10:15:54 +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>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>
Subject: Re: [PATCH v7 05/45] arm64: RME: Add wrappers for RMI calls

On 3/4/25 1:05 AM, Steven Price wrote:
> On 03/03/2025 03:42, Gavin Shan wrote:
>> On 2/14/25 2:13 AM, Steven Price wrote:
>>> The wrappers make the call sites easier to read and deal with the
>>> boiler plate of handling the error codes from the RMM.
>>>
>>> Signed-off-by: Steven Price <steven.price@....com>
>>> ---
>>> Changes from v5:
>>>    * Further improve comments
>>> Changes from v4:
>>>    * Improve comments
>>> Changes from v2:
>>>    * Make output arguments optional.
>>>    * Mask RIPAS value rmi_rtt_read_entry()
>>>    * Drop unused rmi_rtt_get_phys()
>>> ---
>>>    arch/arm64/include/asm/rmi_cmds.h | 508 ++++++++++++++++++++++++++++++
>>>    1 file changed, 508 insertions(+)
>>>    create mode 100644 arch/arm64/include/asm/rmi_cmds.h
>>>
>>
>> With the following nitpicks addressed:
>>
>> Reviewed-by: Gavin Shan <gshan@...hat.com>
> 
> Thanks, there were a couple of other pages and params_ptr references
> that I've updated to granules and just 'params' too now. With hindsight
> conflating pages and granules in the earlier versions of this series was
> a big mistake ;)
> 

Yeah, that was because the assumption was the page size and granule size are
equal(4KB), but they're still different things. With the intention to support
ARM CCA on host with non-aligned page sizes (16KB/64KB), we have to differentiate
granule/page.

Ideally, the granule is only visible to RMI calls and their helpers. An new memory
allocator seems inevitable so that the allocated pages can be distributed on requests
by various RMI helpers in granule. It means the allocator is the line to separate page
and granule :)

Thanks,
Gavin

> Steve
> 
>>> diff --git a/arch/arm64/include/asm/rmi_cmds.h b/arch/arm64/include/
>>> asm/rmi_cmds.h
>>> new file mode 100644
>>> index 000000000000..043b7ff278ee
>>> --- /dev/null
>>> +++ b/arch/arm64/include/asm/rmi_cmds.h
>>> @@ -0,0 +1,508 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +/*
>>> + * Copyright (C) 2023 ARM Ltd.
>>> + */
>>> +
>>> +#ifndef __ASM_RMI_CMDS_H
>>> +#define __ASM_RMI_CMDS_H
>>> +
>>
>> [...]
>>
>>> +
>>> +/**
>>> + * rmi_rec_aux_count() - Get number of auxiliary granules required
>>> + * @rd: PA of the RD
>>> + * @aux_count: Number of pages written to this pointer
>>                    ^^^^^^^^^^^^^^^
>>                    Number of granules
>>> + *
>>> + * A REC may require extra auxiliary pages to be delegated for the
>>> RMM to
>>                                          ^^^^^
>>                                          granules
>>
>>> + * store metadata (not visible to the normal world) in. This function
>>> provides
>>> + * the number of pages that are required.
>>                      ^^^^^
>>                      granules
>>> + *
>>> + * Return: RMI return code
>>> + */
>>> +static inline int rmi_rec_aux_count(unsigned long rd, unsigned long
>>> *aux_count)
>>> +{
>>> +    struct arm_smccc_res res;
>>> +
>>> +    arm_smccc_1_1_invoke(SMC_RMI_REC_AUX_COUNT, rd, &res);
>>> +
>>> +    if (aux_count)
>>> +        *aux_count = res.a1;
>>> +    return res.a0;
>>> +}
>>> +
>>> +/**
>>> + * rmi_rec_create() - Create a REC
>>> + * @rd: PA of the RD
>>> + * @rec: PA of the target REC
>>> + * @params_ptr: PA of REC parameters
>>> + *
>>> + * Create a REC using the parameters specified in the struct
>>> rec_params pointed
>>> + * to by @params_ptr.
>>> + *
>>> + * Return: RMI return code
>>> + */
>>> +static inline int rmi_rec_create(unsigned long rd, unsigned long rec,
>>> +                 unsigned long params_ptr)
>>> +{
>>> +    struct arm_smccc_res res;
>>> +
>>> +    arm_smccc_1_1_invoke(SMC_RMI_REC_CREATE, rd, rec, params_ptr, &res);
>>> +
>>> +    return res.a0;
>>> +}
>>> +
>>
>> 'params_ptr' may be renamed to 'params'.
>>
>>
>> [...]
>>> +#endif /* __ASM_RMI_CMDS_H */
>>
>> Thanks,
>> Gavin
>>
>