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s=arc-20220608; d=hostedemail.com; t=1726060473; a=rsa-sha256; cv=none; b=zmtMX9f7cGZLFp1NtuCE6eaAjkJq78MD7F5UF3hsfn1W72BOSh4EFDvAk0W5eCc1UBTaLd M6U/NH9Fqa7g1hkSbl5dVhjCeA94EpxJPuD0JiyGwCxme8eOHq+qaFyloTQGKI5c4NtTjH qUzpPWIpmSd83ITymYZZsxxjnMEtwPI= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf21.hostedemail.com: domain of dev.jain@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=dev.jain@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 946901007; Wed, 11 Sep 2024 06:16:57 -0700 (PDT) Received: from [10.162.40.31] (e116581.arm.com [10.162.40.31]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E8F663F66E; Wed, 11 Sep 2024 06:16:19 -0700 (PDT) Message-ID: <30eb3546-9e2c-44a6-9485-604dabc96735@arm.com> Date: Wed, 11 Sep 2024 18:46:16 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] mm: Abstract THP allocation To: David Hildenbrand , akpm@linux-foundation.org, willy@infradead.org, kirill.shutemov@linux.intel.com Cc: ryan.roberts@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, mark.rutland@arm.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, jglisse@google.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240911065600.1002644-1-dev.jain@arm.com> <20240911065600.1002644-2-dev.jain@arm.com> <8bc0e51b-0e9b-4eeb-997f-e2a0b1a0c0f8@arm.com> <62df853c-98fb-4900-9cc6-04208e9611c6@arm.com> <1e722a8f-0d07-40d0-aa30-4ee43dff7951@redhat.com> Content-Language: en-US From: Dev Jain In-Reply-To: <1e722a8f-0d07-40d0-aa30-4ee43dff7951@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: F39271C0026 X-Stat-Signature: 7oogp9ey8i7rckrb1ws18ossaw6e6gue X-Rspam-User: X-HE-Tag: 1726060588-477125 X-HE-Meta: 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 zJ59TC+Z 76EsLOz9kREiMNRR1+p1dnt6CZ4D0M20LsYxIJA+H057FlVKCncJ/SH3mgRs4be82l6invS7QlSZ05I8Us8vJy23FC9AWdE8dSBxzsu9NE00Qd5QRxmEo/N27oD7qOheF/B002i9uxrMSxXzRYOn0O6xg/I5TYlj8iTKB4J5cQKjeBYA= 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 9/11/24 18:44, David Hildenbrand wrote: > On 11.09.24 15:05, Dev Jain wrote: >> >> On 9/11/24 18:30, David Hildenbrand wrote: >>> On 11.09.24 14:53, Dev Jain wrote: >>>> >>>> On 9/11/24 14:57, David Hildenbrand wrote: >>>>> On 11.09.24 08:55, Dev Jain wrote: >>>>>> In preparation for the second patch, abstract away the THP >>>>>> allocation >>>>>> logic present in the create_huge_pmd() path, which corresponds to >>>>>> the >>>>>> faulting case when no page is present. >>>>>> >>>>>> There should be no functional change as a result of applying >>>>>> this patch. >>>>>> >>>>> >>>>> [...] >>>>> >>>>>> + >>>>>> +static void map_pmd_thp(struct folio *folio, struct vm_fault *vmf, >>>>>> +            struct vm_area_struct *vma, unsigned long haddr) >>>>>> +{ >>>>>> +    pmd_t entry; >>>>>> + >>>>>> +    entry = mk_huge_pmd(&folio->page, vma->vm_page_prot); >>>>>> +    entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); >>>>>> +    folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE); >>>>>> +    folio_add_lru_vma(folio, vma); >>>>>> +    set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); >>>>>> +    update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); >>>>> >>>>> It's quite weird to see a mixture of haddr and vmf->address, and >>>>> likely this mixture is wrong or not not required. >>>>> >>>>> Looking at arc's update_mmu_cache_pmd() implementation, I cannot see >>>>> how passing in the unaligned address would do the right thing. But >>>>> maybe arc also doesn't trigger that code path ... who knows :) >>>> >>>> If I am reading correctly, arch/arc/mm/tlb.c: update_mmu_cache_pmd() >>>> calls update_mmu_cache_range() which is already expecting an unaligned >>>> address? But... >>> >>> So update_mmu_cache_pmd() calls >>> >>>      update_mmu_cache_range(NULL, vma, addr, &pte, HPAGE_PMD_NR); >>> >>> But update_mmu_cache_range() only aligns it *to page boundary*: >>> >>>      unsigned long vaddr = vaddr_unaligned & PAGE_MASK; >> >> Ah, totally missed that it was PAGE_MASK. Thanks. >>> >>> We obtain the correct hugepage-aligned physical address from the PTE >>> >>>      phys_addr_t paddr = pte_val(*ptep) & PAGE_MASK_PHYS; >>> >>> Then, we look at the offset in our folio >>> >>>      unsigned long offset = offset_in_folio(folio, paddr); >>> >>> And adjust both vaddr and paddr >>> >>>      paddr -= offset; >>>      vaddr -= offset; >>> >>> To then use that combination with >>> >>>      __inv_icache_pages(paddr, vaddr, nr); >>> >>> If I am not wrong, getting a non-hugepage aligned vaddr messes up >>> things here. But only regarding the icache I think. >> >> Looks like it... > > As we are adding a fresh page where there previously wasn't anything > mapped (no icache invaldiation required?), and because most anon > mappings are not executable, maybe that's why nobody notices so far. Thanks for the observation!