From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 EECAF2951C4 for ; Thu, 15 May 2025 08:53:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747299211; cv=none; b=X81YEguo4/z6vBMn+Z5x3paMQIZO0XYifHM54hjO7k5ZLRSLwAFmhqB5TepljlZxUnRmWBUqBTwZQSTH1TBx0HKJoxpAdsGMTECRGqKGmIaB0+c+X6UQhsWc37lOZ99o5Qj+84JLT9XJ0uNVoAc6vcRHCdLOh3zDdtj5HcB+TUg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747299211; c=relaxed/simple; bh=gP5bYnarlJgPCAcYhBxdJqiGMfS3ZlaEJF4D8OrewcI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VKl/ra6DiNpXDrnJDbuHIEYlPD6X463ONqh/IljU2ox8evddBWnayx+Xrohh8de7RynagAEDwPhD6mVMj3VMzh6vwteDISjpwTQVie0a7sQKuJHZvdlynEOBgyT5zOI7+d4EIpAT8bwhAWGWXpf0WY77QMSGtgU7Z6fDN/fb6WQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Fw0bV684; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Fw0bV684" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747299208; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=mxFMYaptLLUT//IK4P864ymdu1SsueZ98Tp1MNq3RV4=; b=Fw0bV684IX7idkVlpRr0+x2vcnBQC3K1w2+2OLIs5k0D/0tLNDIw4QGm5w2jt4796Tm8z2 zH2krEuFNBopjNGpaFdQFd6udHXKKb0IA3eS3VWvibUwQdhFB1cOr86J59E9rWluVQXnjQ 813c9z9shbvPBTYR7oUkMi9bq9n7kaQ= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-22-4LiRdBWCNGCZMR-SDMFrpA-1; Thu, 15 May 2025 04:53:27 -0400 X-MC-Unique: 4LiRdBWCNGCZMR-SDMFrpA-1 X-Mimecast-MFC-AGG-ID: 4LiRdBWCNGCZMR-SDMFrpA_1747299206 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-3a206f05150so456209f8f.0 for ; Thu, 15 May 2025 01:53:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747299206; x=1747904006; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=mxFMYaptLLUT//IK4P864ymdu1SsueZ98Tp1MNq3RV4=; b=YXZpaHTxFvzyZaI5jddCnH/6KEGUS+FUEvkQUJutCu+rmnSFwb0HK01ec+vvR4wUjr Gm+xKGuBc6cGxrYPWxhxjyFfSmasANkknOWN5dXiUbjcB/gDqFuf5UygGXmEfPoMF282 hLpYqcnrSnjSgn1d4ApbDC0TLiTx4BYgmyfCL3QDd+cJ4vB5RuVzJMpxRBKhGDixVmFQ 2Y0NK6wOVpjBMDjaUtdC1fqF+z2peVTqILCvUsWkTbbyxf8VD3WW3n2w4q5Lut/PBCdu NwB76EoNha4eXuZle58FWPhxkqBbzVmeKtTiEQah+HCD1d50kkG996INaQFNHq9oHhnn /6Wg== X-Forwarded-Encrypted: i=1; AJvYcCWxuic7bQfSouiUFSdPmod0cL4Ie7FG1rE2mQ93lAZOB0p/wJVOCT7iiqUTlCWc/BwmfXZkgYlIUDgYt2o=@vger.kernel.org X-Gm-Message-State: AOJu0YxW6v9AeYvEx1cvG1FGfuj6mb/b60vYh1npb2sBAlA3VKH1OY5U Y/f1Ev5i9TYbxSLtkV0bOlEZJFDawe/0IdD9Qt1fw8QQMP/7ZHTij0+kqN5ovux6vaLYDDidhml VbrSl6gp/vkUOrWr6fnt0Y6uPvNWivPqU2p1T8rCcEtTCIqxCqwMrWO3F62zgMQ== X-Gm-Gg: ASbGnct3HkP7puvpPSEL8EVhbljQnpAIPhYb+XaIsqZ37AKwlWhfx64UpojXZRAZ2E1 XjkBYX4M7Zf9aWszgTH8LReBCUv1pBfzrPX29wn+kZVNB1bHwwOSAZAvbyS5wJt7Of5ozHGaORx Xg9LMA0CatrKTC6S+CNUZY6e15yvJUb2of2nm5iQWAxFSZ2BeEkk7Q5DWG9dntRrGWbGk4HJv6I FSQP2xMK76wY3UPJVr/RBL3uwN32VPShwHl0JuL3J2Lfz420VmOOAULIMAcqJmG+75M68BnwX9K 7WRk67UTiiWJXpIFRkBMV15jNQXeENvw3jQrmeirQ00crsrkODUV8HjLs1nPV1XQ8HjY8uWl4aH VMUAU+TTV/6u9dkcz1SrUBV3LZDdf5dPXxZVeX1M= X-Received: by 2002:a5d:588b:0:b0:3a0:b635:ea43 with SMTP id ffacd0b85a97d-3a35374176dmr1365846f8f.33.1747299206221; Thu, 15 May 2025 01:53:26 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEEsJz5zNV7+Zfbrzpouk886RkGlZnICJAg6K6r7C6mHK9QfUY97jHM/U62zf/Yv0DULdBX7w== X-Received: by 2002:a5d:588b:0:b0:3a0:b635:ea43 with SMTP id ffacd0b85a97d-3a35374176dmr1365828f8f.33.1747299205872; Thu, 15 May 2025 01:53:25 -0700 (PDT) Received: from ?IPV6:2003:d8:2f4a:8900:884a:b3af:e3c9:ec88? (p200300d82f4a8900884ab3afe3c9ec88.dip0.t-ipconnect.de. [2003:d8:2f4a:8900:884a:b3af:e3c9:ec88]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a1f5a4c599sm22499647f8f.94.2025.05.15.01.53.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 May 2025 01:53:25 -0700 (PDT) Message-ID: Date: Thu, 15 May 2025 10:53:24 +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] arm64: Check pxd_leaf() instead of !pxd_table() while tearing down page tables To: Dev Jain , catalin.marinas@arm.com, will@kernel.org Cc: ryan.roberts@arm.com, anshuman.khandual@arm.com, mark.rutland@arm.com, yang@os.amperecomputing.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org References: <20250515063450.86629-1-dev.jain@arm.com> <332ecda7-14c4-4dc3-aeff-26801b74ca04@redhat.com> <4904d02f-6595-4230-a321-23327596e085@arm.com> <6fe7848c-485e-4639-b65c-200ed6abe119@redhat.com> <35ef7691-7eac-4efa-838d-c504c88c042b@arm.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <35ef7691-7eac-4efa-838d-c504c88c042b@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 15.05.25 10:47, Dev Jain wrote: > > > On 15/05/25 2:06 pm, David Hildenbrand wrote: >> On 15.05.25 10:22, Dev Jain wrote: >>> >>> >>> On 15/05/25 1:43 pm, David Hildenbrand wrote: >>>> On 15.05.25 08:34, Dev Jain wrote: >>>>> Commit 9c006972c3fe removes the pxd_present() checks because the caller >>>>> checks pxd_present(). But, in case of vmap_try_huge_pud(), the caller >>>>> only >>>>> checks pud_present(); pud_free_pmd_page() recurses on each pmd through >>>>> pmd_free_pte_page(), wherein the pmd may be none. >>>> The commit states: "The core code already has a check for pXd_none()", >>>> so I assume that assumption was not true in all cases? >>>> >>>> Should that one problematic caller then check for pmd_none() instead? >>> >>>   From what I could gather of Will's commit message, my interpretation is >>> that the concerned callers are vmap_try_huge_pud and vmap_try_huge_pmd. >>> These individually check for pxd_present(): >>> >>> if (pmd_present(*pmd) && !pmd_free_pte_page(pmd, addr)) >>>     return 0; >>> >>> The problem is that vmap_try_huge_pud will also iterate on pte entries. >>> So if the pud is present, then pud_free_pmd_page -> pmd_free_pte_page >>> may encounter a none pmd and trigger a WARN. >> >> Yeah, pud_free_pmd_page()->pmd_free_pte_page() looks shaky. >> >> I assume we should either have an explicit pmd_none() check in >> pud_free_pmd_page() before calling pmd_free_pte_page(), or one in >> pmd_free_pte_page(). >> >> With your patch, we'd be calling pte_free_kernel() on a NULL pointer, >> which sounds wrong -- unless I am missing something important. > > Ah thanks, you seem to be right. We will be extracting table from a none > pmd. Perhaps we should still bail out for !pxd_present() but without the > warning, which the fix commit used to do. Right. We just make sure that all callers of pmd_free_pte_page() already check for it. I'd just do something like: diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 8fcf59ba39db7..e98dd7af147d5 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1274,10 +1274,8 @@ int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr) pmd = READ_ONCE(*pmdp); - if (!pmd_table(pmd)) { - VM_WARN_ON(1); - return 1; - } + VM_WARN_ON(!pmd_present(pmd)); + VM_WARN_ON(!pmd_table(pmd)); table = pte_offset_kernel(pmdp, addr); pmd_clear(pmdp); @@ -1305,7 +1303,8 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr) next = addr; end = addr + PUD_SIZE; do { - pmd_free_pte_page(pmdp, next); + if (pmd_present(*pmdp)) + pmd_free_pte_page(pmdp, next); } while (pmdp++, next += PMD_SIZE, next != end); pud_clear(pudp); -- Cheers, David / dhildenb