linux-kernel - Re: [PATCH] arm64: Check pxd_leaf() instead of !pxd

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Message-ID: <332ecda7-14c4-4dc3-aeff-26801b74ca04@redhat.com>
Date: Thu, 15 May 2025 10:13:31 +0200
From: David Hildenbrand <david@...hat.com>
To: Dev Jain <dev.jain@....com>, catalin.marinas@....com, will@...nel.org
Cc: ryan.roberts@....com, anshuman.khandual@....com, mark.rutland@....com,
 yang@...amperecomputing.com, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH] arm64: Check pxd_leaf() instead of !pxd_table() while
 tearing down page tables

On 15.05.25 08:34, Dev Jain wrote:
> Commit 9c006972c3fe removes the pxd_present() checks because the caller
> checks pxd_present(). But, in case of vmap_try_huge_pud(), the caller only
> checks pud_present(); pud_free_pmd_page() recurses on each pmd through
> pmd_free_pte_page(), wherein the pmd may be none.
The commit states: "The core code already has a check for pXd_none()", 
so I assume that assumption was not true in all cases?

Should that one problematic caller then check for pmd_none() instead?

If you were able to trigger this WARN, it's always a good idea to 
include the splat in the commit.

-- 
Cheers,

David / dhildenb