From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1612E385D6B; Thu, 27 Aug 2026 17:07:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787850467; cv=none; b=EscIUGC9gmY/qocRgENyevcCoa4YPWCYLTreedx2XJFhVo55+PsJdyaJjnVVjNyVvIhUFvgbQba3iIOVkSbyZENTEQokfCluhIPMHWkMACG8a7U0PXPT/JKjzQ2sssuG0LxnX9eAk+z96L4u9FC8c1FMdSW+fUEkpIrZRLWLMJ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787850467; c=relaxed/simple; bh=fxigzrezC8cr7rKcepltp+zIdguU7F/EVLGsBJ/Jo/g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kMUTszi0FEesBbmT11qG8Xpw19lueENP66uqRWhLZVVsO0ZosbqgP8g05g2gf6tZUgf7UeDNEUrg7atXUDM3JyxwDFoqBWvDSHdnKvRUj3wGrSF3ryE6aatghpvk0LZnBVRTRMo3Gp2kmBhg9s4BsczqV65MkDRUpB7nW4FLP8U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cpG3+WHr; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cpG3+WHr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E39FF1F000E9; Thu, 27 Aug 2026 17:07:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787850465; bh=7Z6o8710DzidIAipF/VZF9PscAZF/OQSOxpmYRB67qA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=cpG3+WHrJbTUk6ZbVbYSUULv/PzBHhY+6COJiJmNTPFJTKr6aJSWimMlfMvmMnu6P F2R3oOVDJnLy9vt9Awvh2AUDRruAD+t92f9ZLGW4VHZ6CqW2nhJWaF6xFgviPPCyPL dXup5fMDE1HeIDpgjezNcmCLC1xcdq6TbRAE2z86KNgiR4nreCif9Ij1sWdrEahZi/ +pqoBwMQ/LZd9h5nchLgeUifDMhcUX9+pU95sGscOSJIgbxAL1ENTo+SB2NRNYu0Eo uxp2yaS9dj37FaBXFnWeRueqTu+WU2BB9iWVd1joBj52hSJu0chjoiQ/+LDuflsUgh fZfGfIEAvuwdA== Message-ID: <01865a13-2c18-464e-94eb-466613de7bb3@kernel.org> Date: Thu, 27 Aug 2026 19:07:38 +0200 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 2/2] mm/madvise: use vm_normal_folio_pmd() in cold/pageout PMD range To: Gregory Price , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, jannh@google.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, peterx@redhat.com, jgg@ziepe.ca, sashiko-bot , stable@vger.kernel.org References: <20260821144947.167382-1-gourry@gourry.net> <20260821144947.167382-3-gourry@gourry.net> 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 8/21/26 16:49, Gregory Price wrote: > mmap a VM_MIXEDMAP region whose ->huge_fault installs a PMD through > vmf_insert_pfn_pmd() - mshv_vtl_low does this, and needs CAP_SYS_ADMIN to > open - then > > madvise(p, PMD_SIZE, MADV_PAGEOUT); > > With a stand-in module for the driver: > > BUG: unable to handle page fault for address: fffff587c0000008 > RIP: 0010:madvise_cold_or_pageout_pte_range+0x410/0x9b0 > walk_pgd_range+0x52b/0xaf0 > __walk_page_range+0x6a/0x1d0 > walk_page_range_vma_unsafe+0x8e/0x120 > madvise_pageout+0xb2/0x180 > madvise_vma_behavior+0x46b/0xa90 > do_madvise+0x108/0x190 > __x64_sys_madvise+0x26/0x30 > > Nothing validates the pfn on the way in: > > can_madv_lru_vma() rejects VM_PFNMAP, but not VM_MIXEDMAP > can_fault() *pfn = vmf->pgoff & ~(mask >> PAGE_SHIFT); > vmf_insert_pfn_pmd() no pfn_valid() check > pmd_folio() pfn_to_page() -> unpopulated vmemmap > > Even with a valid pfn the path is wrong. The mapping carries no rmap, so > folio_maybe_mapped_shared() sees mapcount 0, and the walker goes on to > folio_deactivate(), or folio_isolate_lru() plus reclaim_pages(), against a > folio this mapping does not own. > > Use vm_normal_folio_pmd() and skip on NULL, as the PTE half of this same > walker already does with vm_normal_folio(). The huge zero PMD is already > handled further up by is_huge_zero_pmd(). The last part doesn't make sense, see below. > > Fixes: 3c8e44c9b369 ("mm: mark special bits for huge pfn mappings when inject") > Reported-by: sashiko-bot > Closes: https://sashiko.dev/#/patchset/20260817220810.1175596-1-gourry%40gourry.net > Cc: # v6.19+ > Assisted-by: Claude:claude-opus-5 > Signed-off-by: Gregory Price (Meta) > --- > mm/madvise.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index ffd6a68320a8..ab362bc482a5 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -393,7 +393,9 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > goto huge_unlock; > } > > - folio = pmd_folio(orig_pmd); > + folio = vm_normal_folio_pmd(vma, addr, orig_pmd); > + if (!folio) > + goto huge_unlock; I think you can now drop the is_huge_zero_pmd() check, because !vm_normal_folio_pmd() includes the huge zero folio. -- Cheers, David