From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-120.mta0.migadu.com [91.218.175.120]) (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 0DB5D3CA487 for ; Tue, 15 Sep 2026 13:43:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.120 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789479809; cv=none; b=mOXYDW2eEUF+1s49jckB/VwPtPXWfex7rsGPE3PdvXR45diuxCXb89szEPD7g3aG+sPQn5w1303RQPtyxq1Kz740aOwm1Du4Tg8f+kcjwENM1pFvE2zx9wO2SGe1MaQUQy1JMQ37mAmiqcsmdj2fvYgTPJU35cnoUkEkh01Mx6I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789479809; c=relaxed/simple; bh=6HudDoiUDG0qD8sOY5Dvp2rvFR5U8GAkB5GWE5aD+1M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=D9vW1QtrwLzCdgERKqcV9jb+yxZtPTzQMxe2guAl5pTXBPGjXL8AiZ0+fM3ybxcp1aJotbWXyxxFzTIcFP1TzrTNc/EV0Kn5RV3NDgcq5Vo4B6375UePTkgGLhdRpTkG7BmxPpk1kXpCHpXmy0C+lMX8MNdNTIW3a8YhQsrPkEA= 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=vGPc+Z92; arc=none smtp.client-ip=91.218.175.120 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="vGPc+Z92" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=6HudDoiUDG0qD8sOY5Dvp2rvFR5U8GAkB5GWE5aD+1M=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789479804; v=1; x=1790084604; b=vGPc+Z92QfmYlv0I08b8/LRhcYnsPy6z35SiQ4jrED23UugUlek7Z4JMvHtx5DvOEE1Kg/Cy IJoObSEawkgGIYk/nI+8LeG2zT64D9bj0dBWndB2mRTbgH2058moz1XmfEASVVy/vOgfYWD/hub oxndnVdWm1uVTzlb1PcgT8/Y= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id abc51d4308209202; Tue, 15 Sep 2026 13:43:23 +0000 X-Mizu-Trace-ID: abc51d4308209202 X-Migadu-Flow: FLOW_OUT Message-ID: <30bcc70c-be07-4237-9bb1-554aa5b5c5c2@linux.dev> Date: Tue, 15 Sep 2026 21:43:15 +0800 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 1/1] mm/huge_memory: fix pgtable withdrawal for huge zero PMDs To: Andrew Morton , Kiryl Shutsemau , "David Hildenbrand (Arm)" Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev, ljs@kernel.org, surenb@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260912234635.db50397364858aa15f58f4d7@linux-foundation.org> <20260913072312.52111-1-lance.yang@linux.dev> <20260914111940.f7e2c72eac4a2df97a646793@linux-foundation.org> Content-Language: en-US From: Lance Yang In-Reply-To: <20260914111940.f7e2c72eac4a2df97a646793@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2026/9/15 02:19, Andrew Morton wrote: > On Mon, 14 Sep 2026 16:29:00 +0200 "David Hildenbrand (Arm)" wrote: > >> On 9/14/26 12:59, Kiryl Shutsemau wrote: >>> On Sun, Sep 13, 2026 at 03:23:12PM +0800, Lance Yang wrote: >>>> >>>> On Sat, Sep 12, 2026 at 11:46:35PM -0700, Andrew Morton wrote: >>>>> >>>>> >>>>> That's the sort of thing we'd prefer to avoid. >>>>> >>>>> >>>>> How real is this? Is there a reported-by:? Do you have a reproducer? >>>> >>>> Yes, I reproduced it on x86 with a small test module. It sets >>>> VM_MIXEDMAP | VM_HUGEPAGE and calls vmf_insert_pfn_pmd() with >>>> huge_zero_pfn, without touching the page tables directly. A full-PMD >>>> munmap() crashes before the split series[1] as well. >>> >>> Ah. So there's no real bug upstream, right? >> >> Matches my understanding. > > Thanks. I'll remove cc:stable, move this into mm-unstable as a > next-merge-window thing. Sounds good to me, thanks, Andrew! Kiryl, David, would you prefer the validation for raw-PFN mappings of the huge zero page as a separate follow-up, or should that validation replace this patch? wdyt Cheers, Lance