linux-kernel - Re: [PATCH v5 12/19] efi: arm64: Map Device with Prot Shared

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Message-ID: <29016e56-e632-422d-a4d2-1891fad2c565@redhat.com>
Date: Tue, 10 Sep 2024 14:15:39 +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 12/19] efi: arm64: Map Device with Prot Shared

On 8/19/24 11:19 PM, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@....com>
> 
> Device mappings need to be emualted by the VMM so must be mapped shared
> with the host.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> Changes since v4:
>   * Reworked to use arm64_is_iomem_private() to decide whether the memory
>     needs to be decrypted or not.
> ---
>   arch/arm64/kernel/efi.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index 712718aed5dd..95f8e8bf07f8 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -34,8 +34,16 @@ static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
>   	u64 attr = md->attribute;
>   	u32 type = md->type;
>   
> -	if (type == EFI_MEMORY_MAPPED_IO)
> -		return PROT_DEVICE_nGnRE;
> +	if (type == EFI_MEMORY_MAPPED_IO) {
> +		pgprot_t prot = __pgprot(PROT_DEVICE_nGnRE);
> +
> +		if (arm64_is_iomem_private(md->phys_addr,
> +					   md->num_pages << EFI_PAGE_SHIFT))
> +			prot = pgprot_encrypted(prot);
> +		else
> +			prot = pgprot_decrypted(prot);
> +		return pgprot_val(prot);
> +	}
>   

Question: the second parameter (@size) passed to arm64_is_iomem_private() covers the
whole region. In [PATCH v5 10/19] arm64: Override set_fixmap_io, the size has been
truncated to the granule size (4KB). They look inconsistent and I don't understand
the reason.

Thanks,
Gavin