linux-kernel - Re: [PATCH v2 06/43] arm64: RME: Add wrappers for RMI calls

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Message-ID: <b8019da1-d361-445b-a224-0761640aa616@arm.com>
Date: Tue, 16 Apr 2024 14:14:37 +0100
From: Suzuki K Poulose <suzuki.poulose@....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>, 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 06/43] arm64: RME: Add wrappers for RMI calls

Hi Steven

On 12/04/2024 09:42, 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.
> 

I have compared the parameters and output values to that of the RMM spec
and they match. There are some minor nits below.

> Signed-off-by: Steven Price <steven.price@....com>
> ---
>   arch/arm64/include/asm/rmi_cmds.h | 509 ++++++++++++++++++++++++++++++
>   1 file changed, 509 insertions(+)
>   create mode 100644 arch/arm64/include/asm/rmi_cmds.h
> 
> diff --git a/arch/arm64/include/asm/rmi_cmds.h b/arch/arm64/include/asm/rmi_cmds.h
> new file mode 100644
> index 000000000000..c21414127e8e
> --- /dev/null
> +++ b/arch/arm64/include/asm/rmi_cmds.h
> @@ -0,0 +1,509 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2023 ARM Ltd.
> + */
> +
> +#ifndef __ASM_RMI_CMDS_H
> +#define __ASM_RMI_CMDS_H
> +
> +#include <linux/arm-smccc.h>
> +
> +#include <asm/rmi_smc.h>
> +
> +struct rtt_entry {
> +	unsigned long walk_level;
> +	unsigned long desc;
> +	int state;
> +	int ripas;
> +};
> +

..

> +/**
> + * rmi_data_destroy() - Destroy a Data Granule
> + * @rd: PA of the RD
> + * @ipa: IPA at which the granule is mapped in the guest
> + * @data_out: PA of the granule which was destroyed
> + * @top_out: Top IPA of non-live RTT entries
> + *
> + * Transitions the granule to DESTROYED state, the address cannot be used by
> + * the guest for the lifetime of the Realm.
> + *
> + * Return: RMI return code
> + */
> +static inline int rmi_data_destroy(unsigned long rd, unsigned long ipa,
> +				   unsigned long *data_out,
> +				   unsigned long *top_out)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_invoke(SMC_RMI_DATA_DESTROY, rd, ipa, &res);
> +
> +	*data_out = res.a1;
> +	*top_out = res.a2;

minor nit: Do we need to be safer by checking the parameters before 
filling them in ? i.e.,

	if (ptr)
		*ptr = result_out;

This applies for others calls below.

> +
> +	return res.a0;
> +}

> +
> +/**
> + * rmi_realm_destroy() - Destroy a Realm
> + * @rd: PA of the RD
> + *
> + * Destroys a Realm, all objects belonging to the Realm must be destroyed first.
> + *
> + * Return: RMI return code
> + */
> +static inline int rmi_realm_destroy(unsigned long rd)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_invoke(SMC_RMI_REALM_DESTROY, rd, &res);
> +
> +	return res.a0;
> +}
> +
> +/**
> + * rmi_rec_aux_count() - Get number of auxiliary Granules required
> + * @rd: PA of the RD
> + * @aux_count: Number of pages written to this pointer
> + *
> + * A REC may require extra auxiliary pages to be delegateed for the RMM to

minor nit: "s/delegateed/delegated/"

..

> +/**
> + * rmi_rtt_read_entry() - Read an RTTE
> + * @rd: PA of the RD
> + * @ipa: IPA for which to read the RTTE
> + * @level: RTT level at which to read the RTTE
> + * @rtt: Output structure describing the RTTE
> + *
> + * Reads a RTTE (Realm Translation Table Entry).
> + *
> + * Return: RMI return code
> + */
> +static inline int rmi_rtt_read_entry(unsigned long rd, unsigned long ipa,
> +				     long level, struct rtt_entry *rtt)
> +{
> +	struct arm_smccc_1_2_regs regs = {
> +		SMC_RMI_RTT_READ_ENTRY,
> +		rd, ipa, level
> +	};
> +
> +	arm_smccc_1_2_smc(&regs, &regs);
> +
> +	rtt->walk_level = regs.a1;
> +	rtt->state = regs.a2 & 0xFF;

minor nit: We mask the state, but not the "ripas". Both of them are u8. 
For consistency, we should mask both or neither.

> +	rtt->desc = regs.a3;
> +	rtt->ripas = regs.a4;
> +
> +	return regs.a0;
> +}
> +

..

> +/**
> + * rmi_rtt_get_phys() - Get the PA from a RTTE
> + * @rtt: The RTTE
> + *
> + * Return: the physical address from a RTT entry.
> + */
> +static inline phys_addr_t rmi_rtt_get_phys(struct rtt_entry *rtt)
> +{
> +	return rtt->desc & GENMASK(47, 12);
> +}

I guess this may need to change with the LPA2 support in RMM and must be
used in conjunction with the "realm" object to make the correct
conversion.


Suzuki


> +
> +#endif