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(p200300d82f32c2009add4a7a46aaf740.dip0.t-ipconnect.de. [2003:d8:2f32:c200:9add:4a7a:46aa:f740]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-440a530a6e9sm128836965e9.16.2025.04.28.09.16.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Apr 2025 09:16:23 -0700 (PDT) Message-ID: <7a26e29c-d889-450a-a5e1-ce671f09e4c8@redhat.com> Date: Mon, 28 Apr 2025 18:16:21 +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 v1 05/11] mm: convert VM_PFNMAP tracking to pfnmap_track() + pfnmap_untrack() To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Andrew Morton , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato References: <20250425081715.1341199-1-david@redhat.com> <20250425081715.1341199-6-david@redhat.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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 28.04.25 18:08, Peter Xu wrote: > On Fri, Apr 25, 2025 at 10:36:55PM +0200, David Hildenbrand wrote: >> On 25.04.25 22:23, Peter Xu wrote: >>> On Fri, Apr 25, 2025 at 10:17:09AM +0200, David Hildenbrand wrote: >>>> Let's use our new interface. In remap_pfn_range(), we'll now decide >>>> whether we have to track (full VMA covered) or only sanitize the pgprot >>>> (partial VMA covered). >>>> >>>> Remember what we have to untrack by linking it from the VMA. When >>>> duplicating VMAs (e.g., splitting, mremap, fork), we'll handle it similar >>>> to anon VMA names, and use a kref to share the tracking. >>>> >>>> Once the last VMA un-refs our tracking data, we'll do the untracking, >>>> which simplifies things a lot and should sort our various issues we saw >>>> recently, for example, when partially unmapping/zapping a tracked VMA. >>>> >>>> This change implies that we'll keep tracking the original PFN range even >>>> after splitting + partially unmapping it: not too bad, because it was >>>> not working reliably before. The only thing that kind-of worked before >>>> was shrinking such a mapping using mremap(): we managed to adjust the >>>> reservation in a hacky way, now we won't adjust the reservation but >>>> leave it around until all involved VMAs are gone. >>>> >>>> Signed-off-by: David Hildenbrand >>>> --- >>>> include/linux/mm_inline.h | 2 + >>>> include/linux/mm_types.h | 11 ++++++ >>>> kernel/fork.c | 54 ++++++++++++++++++++++++-- >>>> mm/memory.c | 81 +++++++++++++++++++++++++++++++-------- >>>> mm/mremap.c | 4 -- >>>> 5 files changed, 128 insertions(+), 24 deletions(-) >>>> >>>> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h >>>> index f9157a0c42a5c..89b518ff097e6 100644 >>>> --- a/include/linux/mm_inline.h >>>> +++ b/include/linux/mm_inline.h >>>> @@ -447,6 +447,8 @@ static inline bool anon_vma_name_eq(struct anon_vma_name *anon_name1, >>>> #endif /* CONFIG_ANON_VMA_NAME */ >>>> +void pfnmap_track_ctx_release(struct kref *ref); >>>> + >>>> static inline void init_tlb_flush_pending(struct mm_struct *mm) >>>> { >>>> atomic_set(&mm->tlb_flush_pending, 0); >>>> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >>>> index 56d07edd01f91..91124761cfda8 100644 >>>> --- a/include/linux/mm_types.h >>>> +++ b/include/linux/mm_types.h >>>> @@ -764,6 +764,14 @@ struct vma_numab_state { >>>> int prev_scan_seq; >>>> }; >>>> +#ifdef __HAVE_PFNMAP_TRACKING >>>> +struct pfnmap_track_ctx { >>>> + struct kref kref; >>>> + unsigned long pfn; >>>> + unsigned long size; >>>> +}; >>>> +#endif >>>> + >>>> /* >>>> * This struct describes a virtual memory area. There is one of these >>>> * per VM-area/task. A VM area is any part of the process virtual memory >>>> @@ -877,6 +885,9 @@ struct vm_area_struct { >>>> struct anon_vma_name *anon_name; >>>> #endif >>>> struct vm_userfaultfd_ctx vm_userfaultfd_ctx; >>>> +#ifdef __HAVE_PFNMAP_TRACKING >>>> + struct pfnmap_track_ctx *pfnmap_track_ctx; >>>> +#endif >>> >>> So this was originally the small concern (or is it small?) that this will >>> grow every vma on x86, am I right? >> >> Yeah, and last time I looked into this, it would have grown it such that it would >> require a bigger slab. Right now: > > Probably due to what config you have. E.g., when I'm looking mine it's > much bigger and already consuming 256B, but it's because I enabled more > things (userfaultfd, lockdep, etc.). Note that I enabled everything that you would expect on a production system (incld. userfaultfd, mempolicy, per-vma locks), so I didn't enable lockep. Thanks for verifying! -- Cheers, David / dhildenb