From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-7.mta0.migadu.com [91.218.175.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C6E8F37F319 for ; Sat, 10 Oct 2026 03:50:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791604242; cv=none; b=UwJ3V9+Or7doEIUalkcttxGIlF+zfcfWK7msP6Nn8RNC1MIS7Jon534RD7sFrFXA7p/14CSZDmv7C1p2Z0Eeevsm04kZCE2Arutfi7Pb7p8KDL+7nGUoGQRF8wYBYlkQ5tSuxziUrhxH/uVWzMezf6mjb+TS70r43rRTnS+Mujg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791604242; c=relaxed/simple; bh=ejj+1mQ7GORhSID6jODIShDthWwWtiPSHyMLfZ3/AqU=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=HBchn792IiEbSOzl0GVqawNzO/01KfthVhJSdrwgcneyk3BjzV6RSgrGskEegf4H/VNJYscyQFzEcO4IlTixgfqA19BBL9H5L/6gBmfjFL91bI93MYUIVMWFBHh0VkUZ+HgbXSrpLwfdPlzmTztQuKf3Xu9/maA/AO1RN2H4t0M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=oXXbzJ4J; arc=none smtp.client-ip=91.218.175.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="oXXbzJ4J" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=ejj+1mQ7GORhSID6jODIShDthWwWtiPSHyMLfZ3/AqU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791604238; v=1; x=1792209038; b=oXXbzJ4JEVIIlXmLSFRm9OK+stur3MstaTSM8R7gazaCRKIGrKwCfpn8L2p7Dj5L16p8FS71 p+ORylMMHzgTMoR/YNm9X2+lSyxkj632ly8gHzZ2g0ei1Jyxvu/lJPvz/2amZ+UA2nLFH41br1x pIxXRgA80hDqODcHgG5tXZrI= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 9484aa877343ee44; Sat, 10 Oct 2026 03:50:15 +0000 X-Mizu-Trace-ID: 9484aa877343ee44 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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: <39ae6c48-7fcc-41d5-bfaf-fe626071861e@kernel.org> Date: Sat, 10 Oct 2026 11:49:57 +0800 Cc: Muchun Song , akpm@linux-foundation.org, linux-mm@kvack.org, stable@vger.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: <98481914-D123-4F58-97FA-C2F34469D34C@linux.dev> References: <20261008073021.2512665-1-songmuchun@bytedance.com> <20261008073021.2512665-2-songmuchun@bytedance.com> <39ae6c48-7fcc-41d5-bfaf-fe626071861e@kernel.org> To: "David Hildenbrand (Arm)" X-Mailer: Apple Mail (2.3901.100.1.1.12) > On Oct 10, 2026, at 04:36, David Hildenbrand (Arm) = wrote: >=20 > On 10/9/26 22:33, David Hildenbrand (Arm) wrote: >> On 10/8/26 09:30, Muchun Song wrote: >>> 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)); >>> else >>> pagetable_free(page_ptdesc(page)); >>> } >>=20 >> pagetable_free() will do ptdesc_test_kernel(pt) -> = pagetable_free_kernel(pt) -> >> pagetable_dtor_free(). >=20 > Ah, behavior depends on CONFIG_ASYNC_KERNEL_PGTABLE_FREE$ ... >=20 > Why not do the right thing in pagetable_free() instead? Good point. More easy to this issue on different architecture. I'll fix pagetable_free next version. Thanks, Muchun >=20 > --=20 > Cheers, >=20 > David