From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 50D31CA6007 for ; Thu, 8 Oct 2026 08:33:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:To:References:Message-Id: Content-Transfer-Encoding:Cc:Date:In-Reply-To:From:Subject:Mime-Version: Content-Type:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/mfZx2zinbwawb2SikdYr4parys9Z5tteYIz1sprlF4=; b=RvgkomWb8YowUJm5AAC/h5mAJq yQVyQ23P7Wa79pQ1DpP2VsxBjx6fmLbkRM+EBi7v3GRugQtzRS8Ok4SmgNz/6YFoXKl2QzgRqLVwr nCuWExAkGcsST6CaDxgEfW9vg6y0XzlnPa+qhNX1fOw7RNdpVWz+qyqdqFmdXYA6C/I2LcnK/d2nD 0+6rMYwU0n6IGgVJU16sm6JQ7RtM+Ss8xBYX/QkbHRZMfunPHrmrdwqWUis507PvJtJoboIueII92 4ARARYbi8ytnTgDSyVHcqPWqFXQKsqVGxN5PtUWikYjlymUcceiqTnk3SgIlB+j2zDfyoYAJJtKjD FiQrwz8g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xEjZ1-00000003sz6-0PZw; Thu, 08 Oct 2026 08:33:19 +0000 Received: from out-96.mta0.migadu.com ([2001:41d0:1004:224b::60] helo=mta0.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xEjYy-00000003sxX-3Ms6 for linux-arm-kernel@lists.infradead.org; Thu, 08 Oct 2026 08:33:18 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=HyGwwSVmXvhmOZPb5rYhVyPJ+UvfVubhGgu9kDF0uic=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791448393; v=1; x=1792053193; b=BJaTmY9Q2AcNcg0Ibm4M/yFMd0jOkbvaF9GOOHOQC2F0NG/5vtTQRpNkUTdl7umzZkowp+Zg saCqstM8QnCXhqR6BV3oExuPa4vjItORXe5J2PfzMk0ZL5l8xXlY7kZNQe2GdUuhgcJlYN7Wbb3 gFKgnhcpnbQTV25OLuzBl/PM= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id f276eb58ea604195; Thu, 08 Oct 2026 08:33:13 +0000 X-Mizu-Trace-ID: f276eb58ea604195 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.100.1.1.12\)) Subject: Re: [PATCH 1/4] x86/mm: fix missing pgtable destructor for vmemmap tables From: Muchun Song In-Reply-To: <20261008073021.2512665-2-songmuchun@bytedance.com> Date: Thu, 8 Oct 2026 10:32:58 +0200 Cc: akpm@linux-foundation.org, linux-mm@kvack.org, stable@vger.kernel.org, david@kernel.org, osalvador@suse.de, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, linux-riscv@lists.infradead.org, agordeev@linux.ibm.com, kevin.brodsky@arm.com, bjorn@rivosinc.com, apopple@nvidia.com, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20261008073021.2512665-1-songmuchun@bytedance.com> <20261008073021.2512665-2-songmuchun@bytedance.com> To: Muchun Song X-Mailer: Apple Mail (2.3901.100.1.1.12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261008_013317_048829_56532FCE X-CRM114-Status: GOOD ( 16.55 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > On Oct 8, 2026, at 09:30, Muchun Song = wrote: >=20 > Since commit 49f599666420 ("mm: call ctor/dtor for kernel PTEs"), > pte_alloc_one_kernel() runs the page-table constructor for kernel PTE > tables. >=20 > HugeTLB vmemmap optimization uses pte_alloc_one_kernel() when = splitting > a PMD. Restoring the vmemmap backing pages does not collapse the PTE > table, so a later memory hot-remove eventually frees that table = through > free_pagetable(). That path currently calls pagetable_free() directly > without decrementing NR_PAGETABLE. >=20 > Use PageTable() to identify constructor-backed tables and run the > matching destructor before freeing them. Keep reserved and > constructor-free tables on their existing paths. This also prepares > vmemmap teardown for generic runtime allocations through the normal > pgalloc helpers. >=20 > Fixes: 49f599666420 ("mm: call ctor/dtor for kernel PTEs") > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: Muchun Song > --- > arch/x86/mm/init_64.c | 2 ++ > 1 file changed, 2 insertions(+) >=20 > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index 70e682180291..a3ea627157ab 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -1003,6 +1003,8 @@ static void __meminit free_pagetable(struct page = *page) > { > if (PageReserved(page)) > free_reserved_page(page); > + else if (PageTable(page)) > + pagetable_dtor_free(page_ptdesc(page)); Sashiko mentioned that kernel page table pages and vmemmap pages are freed to the buddy allocator before their parent entries are cleared and before the TLB is flushed, creating a dangling pointer window. That's a a real but pre-existing issue, I will not fix that in this series. > else > pagetable_free(page_ptdesc(page)); > } > --=20 > 2.54.0 >=20