linux-kernel - Re: [PATCH v2 1/3] x86/devmem: Remove duplicate range_is

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Message-ID: <680147f6b6411_130fd294c2@dwillia2-mobl3.amr.corp.intel.com.notmuch>
Date: Thu, 17 Apr 2025 11:27:02 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Naveen N Rao <naveen@...nel.org>, Dan Williams <dan.j.williams@...el.com>
CC: <dave.hansen@...ux.intel.com>, Ingo Molnar <mingo@...nel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] x86/devmem: Remove duplicate range_is_allowed()
 definition

Naveen N Rao wrote:
[..]
> > The pat_enabled check was originally added as a *bypass* of additional
> > logic in phys_mem_access_prot_allowed() [1] to validate that /dev/mem was
> > establishing compatible mappings of "System-RAM" via /dev/mem. This
> > patch maintains that expectation that phys_mem_access_prot_allowed()
> > returns immediately when there is no potential cache conflict.
> 
> Thanks for the background, that makes sense.
> 
> Do we also no longer need the devmem_is_allowed() checks in pat.c if PAT 
> is enabled and !CONFIG_STRICT_DEVMEM?

The only one that is left is the one in phys_mem_access_prot_allowed()
and that one properly compiles away to nothing in the
!CONFIG_STRICT_DEVMEM case.