linux-kernel - Re: [PATCH v2 06/14] arm64: Override set_fixmap

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Message-ID: <ZkI8TZmEKwrEKhe_@arm.com>
Date: Mon, 13 May 2024 17:14:05 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Steven Price <steven.price@....com>
Cc: kvm@...r.kernel.org, kvmarm@...ts.linux.dev,
	Suzuki K Poulose <suzuki.poulose@....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 06/14] arm64: Override set_fixmap_io

On Fri, Apr 12, 2024 at 09:42:05AM +0100, Steven Price wrote:
> 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.
> Future changes could filter the physical address and make the
> decision accordingly.
[...]
> +void set_fixmap_io(enum fixed_addresses idx, phys_addr_t phys)
> +{
> +	pgprot_t prot = FIXMAP_PAGE_IO;
> +
> +	/*
> +	 * For now we consider all I/O as non-secure. For future
> +	 * filter the I/O base for setting appropriate permissions.
> +	 */
> +	prot = __pgprot(pgprot_val(prot) | PROT_NS_SHARED);
> +
> +	return __set_fixmap(idx, phys, prot);
> +}

I looked through the patches and could not find any place where this
function does anything different as per the commit log suggestion. Can
we just update FIXMAP_PAGE_IO for now until you have a clear use-case?

-- 
Catalin