linux-kernel - Re: [PATCH 3/4] x86/mm: Inhibit _PAGE_NX changes from cpa_process

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Date:   Mon, 14 Nov 2022 08:08:16 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        oliver.sang@...el.com
Subject: Re: [PATCH 3/4] x86/mm: Inhibit _PAGE_NX changes from
 cpa_process_alias()

On 11/10/22 04:52, Peter Zijlstra wrote:
> There is a cludge in change_page_attr_set_clr() that inhibits
> propagating NX changes to the aliases (directmap and highmap) -- this
> is a cludge twofold:
> 
>  - it also inhibits the primary checks in __change_page_attr();
>  - it hard depends on single bit changes.
> 
> The introduction of set_memory_rox() triggered this last issue for
> clearing both _PAGE_RW and _PAGE_NX.
> 
> Explicitly ignore _PAGE_NX in cpa_process_alias() instead.
> 
> Fixes: b38994948567 ("x86/mm: Implement native set_memory_rox()")
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Debugged-by: Dave Hansen <dave.hansen@...el.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Looks sane.  It's also nice how the checkalias stuff continues to fall
out of there.

Acked-by: Dave Hansen <dave.hansen@...el.com>