linux-kernel - Re: [PATCH v5 07/19] arm64: rsi: Add support for checking whether an MMIO is protected

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Message-ID: <a64defd3-d202-4b65-9ebb-46821717cf20@redhat.com>
Date: Tue, 10 Sep 2024 13:51:12 +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>
Subject: Re: [PATCH v5 07/19] arm64: rsi: Add support for checking whether an
 MMIO is protected

On 8/19/24 11:19 PM, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@....com>
> 
> On Arm CCA, with RMM-v1.0, all MMIO regions are shared. However, in
> the future, an Arm CCA-v1.0 compliant guest may be run in a lesser
> privileged partition in the Realm World (with Arm CCA-v1.1 Planes
> feature). In this case, some of the MMIO regions may be emulated
> by a higher privileged component in the Realm world, i.e, protected.
> 
> Thus the guest must decide today, whether a given MMIO region is shared
> vs Protected and create the stage1 mapping accordingly. On Arm CCA, this
> detection is based on the "IPA State" (RIPAS == RIPAS_IO). Provide a
> helper to run this check on a given range of MMIO.
> 
> Also, provide a arm64 helper which may be hooked in by other solutions.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> New patch for v5
> ---
>   arch/arm64/include/asm/io.h       |  8 ++++++++
>   arch/arm64/include/asm/rsi.h      |  3 +++
>   arch/arm64/include/asm/rsi_cmds.h | 21 +++++++++++++++++++++
>   arch/arm64/kernel/rsi.c           | 26 ++++++++++++++++++++++++++
>   4 files changed, 58 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
> index 1ada23a6ec19..a6c551c5e44e 100644
> --- a/arch/arm64/include/asm/io.h
> +++ b/arch/arm64/include/asm/io.h
> @@ -17,6 +17,7 @@
>   #include <asm/early_ioremap.h>
>   #include <asm/alternative.h>
>   #include <asm/cpufeature.h>
> +#include <asm/rsi.h>
>   
>   /*
>    * Generic IO read/write.  These perform native-endian accesses.
> @@ -318,4 +319,11 @@ extern bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,
>   					unsigned long flags);
>   #define arch_memremap_can_ram_remap arch_memremap_can_ram_remap
>   
> +static inline bool arm64_is_iomem_private(phys_addr_t phys_addr, size_t size)
> +{
> +	if (unlikely(is_realm_world()))
> +		return arm64_rsi_is_protected_mmio(phys_addr, size);
> +	return false;
> +}
> +

I guess it might be better to unify the function names here. The name of
arm64_is_iomem_private() indicates the IO region is private, while the
name of arm64_rsi_is_protected_mmio() indicates the IO region is protected.
I think it would be nice to rename arm64_is_iomem_private() arm64_is_protected_iomem(),
or rename arm64_rsi_is_protected_mmio() to arm64_rsi_is_private_iomem().

Thanks,
Gavin