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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 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. 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8185140008 X-Stat-Signature: yruzt5ugn1yrxjass46qi4nxeq3hqjhf X-HE-Tag: 1745856987-835572 X-HE-Meta: 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 IuBGKStV ydSOJxiLk1rAr4Q5fnykRsFlVS+Dg7BOBouQ8SX40w9tMK5I4bzKdzLnVXpaTkGmRqLnYYdZSKq6QfjTxduemm/Ma3keSWVxRYnD7dpprFu+03FDGAZ4d08yYjcRYK+WB3ysX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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