From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0DF9B37416E for ; Fri, 27 Feb 2026 20:55:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772225724; cv=none; b=rbgduLbsLmi+5+Fqs1FO/PFLcqX1ORIElxCiZiYEgGgC0KA7M5H8D5iCVXW8H+yVsprXoc0MN3kfFODifPFgmT8S0sBEMb9xUwt8XJLL9YSaJu2ssNhCqKVv7xAndy82r8plR2BWKtntvhrhID1JOofR2QN1yedeNYpsnSmX27U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772225724; c=relaxed/simple; bh=AWTR2K3dBXApAFBSFFqFKURejpZca+nk5sb7sA2btn4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=E4sFW5FXYDsXtjE47ZS2m0cQbHtDFicV1nRHtwwyyoC9XflEPQtqAnzyhzDZOOsy/k7wjBkOOn8HdL8C9eUzuZHyNl2nXXcniKvbsL+Ncj/yVKTrpvhjwG0JbxZEuxV06PJYAVwnDAMj2gKskk8999cXcMdm3Be8zbIhB3k+TtQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pOXn5XWE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pOXn5XWE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8E545C116C6; Fri, 27 Feb 2026 20:55:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772225723; bh=AWTR2K3dBXApAFBSFFqFKURejpZca+nk5sb7sA2btn4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=pOXn5XWEcNoi0kYL+zqUzWF1ShgtL9v4L49YHqamUKLPOS5dtEVajb96mplr9Sbm8 yJQKqwE2l+kmf1oUWqMj+mx0dFXHPbo2TurFgO+o2e62qIxcy5fG22NHBZkoGmhlox mScGjjtimSHCSHDcu7uMjRAdKE8vLsrFohYmIiPIiOfpARyT0IEScy1f0yHnw1nyjr qdVXVx+W4+2ZLNi+XQ8EqTFfrbmFupYKgBoj+ECnPCLQxfutqCfCxVj21dKURnzdBN h3bPcjGOyw0YyoHXP+hq3VPfe8RGbpyBYS9ZoMZNJ/jt0WnAkP+ip0G9UgRonJDzK2 akxm3aT6u+I7A== Message-ID: Date: Fri, 27 Feb 2026 21:55:20 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/debug_vm_pgtable: Replace WRITE_ONCE() with pxd_clear() To: Anshuman Khandual , linux-mm@kvack.org Cc: Andrew Morton , linux-kernel@vger.kernel.org, Ryan Roberts References: <20260227061204.2215395-1-anshuman.khandual@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/27/26 07:12, Anshuman Khandual wrote: > Replace WRITE_ONCE() with generic pxd_clear() to clear out the page table > entries as required. Besides this does not cause any functional change as > well. > > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Suggested-by: Ryan Roberts > Signed-off-by: Anshuman Khandual > --- > Applies on mm-unstable and tested only on arm64 platform. > > mm/debug_vm_pgtable.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 83cf07269f13..23dc3ee09561 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -445,7 +445,7 @@ static void __init pmd_huge_tests(struct pgtable_debug_args *args) > * X86 defined pmd_set_huge() verifies that the given > * PMD is not a populated non-leaf entry. > */ > - WRITE_ONCE(*args->pmdp, __pmd(0)); > + pmd_clear(args->pmdp); > WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot)); > WARN_ON(!pmd_clear_huge(args->pmdp)); > pmd = pmdp_get(args->pmdp); > @@ -465,7 +465,7 @@ static void __init pud_huge_tests(struct pgtable_debug_args *args) > * X86 defined pud_set_huge() verifies that the given > * PUD is not a populated non-leaf entry. > */ > - WRITE_ONCE(*args->pudp, __pud(0)); > + pud_clear(args->pudp); > WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot)); > WARN_ON(!pud_clear_huge(args->pudp)); > pud = pudp_get(args->pudp); On some architectures, pmd_clear() does not set the pmd to zero. See s390x as an example: set_pmd(pmdp, __pmd(_SEGMENT_ENTRY_EMPTY)); Which results on 0x20 being set. Maybe we're lucky and all relevant architectures do not have CONFIG_HAVE_ARCH_HUGE_VMAP. Or maybe it just doesn't matter. We'll find out :) Acked-by: David Hildenbrand (Arm) -- Cheers, David