linux-kernel - Re: [PATCH] mm/ioremap: Pass pgprot_t to ioremap

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Message-ID: <Z7XF4Y3FIbSrSP9u@arm.com>
Date: Wed, 19 Feb 2025 11:52:01 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-mm@...ck.org, Ryan Roberts <ryan.roberts@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-snps-arc@...ts.infradead.org, linux-riscv@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-parisc@...r.kernel.org,
	linux-csky@...r.kernel.org, linux-mips@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-arch@...r.kernel.org,
	loongarch@...ts.linux.dev, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/ioremap: Pass pgprot_t to ioremap_prot() instead of
 unsigned long

On Tue, Feb 18, 2025 at 03:49:54PM +0530, Anshuman Khandual wrote:
> From: Ryan Roberts <ryan.roberts@....com>
> 
> ioremap_prot() currently accepts pgprot_val parameter as an unsigned long,
> thus implicitly assuming that pgprot_val and pgprot_t could never be bigger
> than unsigned long. But this assumption soon will not be true on arm64 when
> using D128 pgtables. In 128 bit page table configuration, unsigned long is
> 64 bit, but pgprot_t is 128 bit.
> 
> Passing platform abstracted pgprot_t argument is better as compared to size
> based data types. Let's change the parameter to directly pass pgprot_t like
> another similar helper generic_ioremap_prot().
> 
> Without this change in place, D128 configuration does not work on arm64 as
> the top 64 bits gets silently stripped when passing the protection value to
> this function.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-snps-arc@...ts.infradead.org
> Cc: linux-riscv@...ts.infradead.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-parisc@...r.kernel.org
> Cc: linux-csky@...r.kernel.org
> Cc: linux-mips@...r.kernel.org
> Cc: linux-s390@...r.kernel.org
> Cc: linux-arch@...r.kernel.org
> Cc: loongarch@...ts.linux.dev
> Cc: linux-sh@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> Co-developed-by: Anshuman Khandual <anshuman.khandual@....com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>

For arm64:

Acked-by: Catalin Marinas <catalin.marinas@....com>