linux-kernel - Re: [PATCH v5 10/19] arm64: Override set_fixmap

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Message-ID: <13bc77b7-5f68-44ca-93ce-578ffe029437@arm.com>
Date: Mon, 19 Aug 2024 15:13:19 +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>,
 Gavin Shan <gshan@...hat.com>, Shanker Donthineni <sdonthineni@...dia.com>,
 Alper Gun <alpergun@...gle.com>
Subject: Re: [PATCH v5 10/19] arm64: Override set_fixmap_io

On 19/08/2024 14:19, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@....com>
> 
> Override the set_fixmap_io to set shared permission for the host
> in case of a CC guest. For now we mark it shared unconditionally.
> 
> If/when support for device assignment and device emulation in the realm
> is added in the future then this will need to filter the physical
> address and make the decision accordingly.
> 
> 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/fixmap.h |  2 ++
>   arch/arm64/mm/mmu.c             | 17 +++++++++++++++++
>   2 files changed, 19 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
> index 87e307804b99..2c20da3a468c 100644
> --- a/arch/arm64/include/asm/fixmap.h
> +++ b/arch/arm64/include/asm/fixmap.h
> @@ -108,6 +108,8 @@ void __init early_fixmap_init(void);
>   #define __late_clear_fixmap(idx) __set_fixmap((idx), 0, FIXMAP_PAGE_CLEAR)
>   
>   extern void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
> +#define set_fixmap_io set_fixmap_io
> +void set_fixmap_io(enum fixed_addresses idx, phys_addr_t phys);
>   
>   #include <asm-generic/fixmap.h>
>   
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 353ea5dc32b8..06b66c23c124 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1193,6 +1193,23 @@ void vmemmap_free(unsigned long start, unsigned long end,
>   }
>   #endif /* CONFIG_MEMORY_HOTPLUG */
>   
> +void set_fixmap_io(enum fixed_addresses idx, phys_addr_t phys)
> +{
> +	pgprot_t prot = FIXMAP_PAGE_IO;
> +
> +	/*
> +	 * The set_fixmap_io maps a single Page covering phys.
> +	 * To make better decision, we stick to the smallest page
> +	 * size supported (4K).
> +	 */
> +	if (!arm64_is_iomem_private(phys, SZ_4K))
> +		prot = pgprot_decrypted(prot);
> +	else
> +		prot = pgprot_encrypted(prot);

With the ioremap_prot_hook introduction, this one looks like should use
that, instead of open coding the same thing. Thoughts ?

Suzuki