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[87.161.174.200]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-447f78aeb7fsm227357165e9.26.2025.05.26.02.38.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 May 2025 02:38:18 -0700 (PDT) Message-ID: Date: Mon, 26 May 2025 11:38:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: reply: [RFC] pin_user_pages_fast failure count increased To: Hyesoo Yu , Zhaoyang Huang Cc: John Hubbard , jaewon31.kim@samsung.com, "zhaoyang.huang@unisoc.com" , "surenb@google.com" , "Steve.Kang@unisoc.com" , Jaewon Kim , "linux-mm@kvack.org" , janghyuck.kim@samsung.com References: <99ae448a-5c5e-4491-8cf7-1325f47e225e@redhat.com> <20250522130901epcms1p31d757b179fbb3563cad6bef4a1829235@epcms1p3> <20250522144418epcms1p2a31c1a5c95b1937077bddf1b30495e83@epcms1p2> <20250523023709epcms1p236d4f55b79adb9366ec1cf6d5792b06b@epcms1p2> <4e2305d6-b067-4963-b16a-367a254d22c1@nvidia.com> <20250526074845.GA2848800@tiffany> <20250526093258.GA3489925@tiffany> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 2EC0440005 X-Stat-Signature: rwckstu9ao6qmhw9ijsdmngwfgpp5r18 X-Rspam-User: X-HE-Tag: 1748252303-553570 X-HE-Meta: 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 PPviqkdL 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 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 26.05.25 11:33, Hyesoo Yu wrote: > On Mon, May 26, 2025 at 04:05:16PM +0800, Zhaoyang Huang wrote: >> On Mon, May 26, 2025 at 3:50 PM Hyesoo Yu wrote: >>> >>> On Thu, May 22, 2025 at 07:52:41PM -0700, John Hubbard wrote: >>>> On 5/22/25 7:37 PM, 김재원 wrote: >>>> ... >>>>> I think this is what you meant, please let me know if you have an idea to make this nicer. >>>>> We may be to able to prepare the patch next week. >>>>> >>>>> static long >>>>> check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs) >>>>> { >>>>> + bool any_unpinnable; >>>>> LIST_HEAD(movable_folio_list); >>>>> >>>>> - collect_longterm_unpinnable_folios(&movable_folio_list, pofs); >>>>> - if (list_empty(&movable_folio_list)) >>>>> - return 0; >>>>> + any_unpinnable = collect_longterm_unpinnable_folios(&movable_folio_list, pofs); >>>>> + if (list_empty(&movable_folio_list)) { >>>>> + if (any_unpinnable) >>>>> + pofs_unpin(pofs); >>>> >>>> I think this is correct, although as I mentioned in the other thread, >>>> that implies that commit 1aaf8c122918 (which didn't add nor remove >>>> any pof unpinning) is probably not the true or only culprit, right? >>>> >>>>> + return any_unpinnable ? -EAGAIN : 0; >>>> >>>> Ha, the "?" operator almost always does more harm than good. >>>> >>>> Here, for example, it has obscured from you the fact that any_unpinnable >>>> is being checked twice, when you could have merged those into a single "if". >>>> >>> >>> Hello, >>> >>> I was wondering if the original problem - an infinite loop when pages allocated by >>> cma_alloc() in vm_ops->fault are passed to GUP - still remains unresolved. >>> (To be honest, I'm not quite sure how such pages end up being pinned via GUP. >>> Is that the expected behavior, or could it possibly indicate a bug ?) >> The original problem arises from applying CMA as guestOS's memory >> slots for kvm which use GUP to setup its 2nd stage mapping(HVA->PFN). >> You can check KVM code if you are interested. >> > > Thanks for the kind explanation. While I'm not deeply familiar with KVM, my understanding > is that there are cases where GUP is used on CMA. > > So does that mean pinning memory from the CMA was actually intended to succeed ? Careful: KVM uses ordinary GUP, not GUP-longterm. -- Cheers, David / dhildenb