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[104.194.78.75]) by smtp.gmail.com with ESMTPSA id 00721157ae682-78fa72b48efsm8363757b3.51.2025.12.18.06.16.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Dec 2025 06:16:31 -0800 (PST) Message-ID: <4249e49a-c91a-4e9c-92c1-79c272627540@gmail.com> Date: Thu, 18 Dec 2025 22:16:05 +0800 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/2] mm/pgtable: use ptdesc for pmd_huge_pte To: "David Hildenbrand (Red Hat)" , alexs@kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , "David S . Miller" , Andreas Larsson , Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Thomas Huth , Will Deacon , Matthew Wilcox , Magnus Lindholm , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org References: <20251214065546.156209-1-alexs@kernel.org> <52e2c1eb-67cf-41ee-9088-760fb6258153@gmail.com> Content-Language: en-US From: Alex Shi In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/12/18 18:01, David Hildenbrand (Red Hat) wrote: > On 12/15/25 01:53, Alex Shi wrote: >> >> >> On 2025/12/14 14:55, alexs@kernel.org wrote: >>> From: Alex Shi >>> >>> 'pmd_huge_pte' are pgtable variables, but used 'pgtable->lru' >>> instead of pgtable->pt_list in pgtable_trans_huge_deposit/withdraw >>> functions, That's a bit weird. >>> >>> So let's convert the pgtable_t to precise 'struct ptdesc *' for >>> ptdesc->pmd_huge_pte, and mm->pmd_huge_pte, then convert function >>> pgtable_trans_huge_deposit() to use correct ptdesc. >>> >>> This convertion works for most of arch, but failed on s390/sparc/powerpc >>> since they use 'pte_t *' as pgtable_t. Is there any suggestion for these >>> archs? If we could have a solution, we may remove the pgtable_t for >>> other >>> archs. >> >> If s390/sparc/powerpc can't align pgtable_t with others, we have to keep >> the pgtable_t to bridge different types. But we could take step to >> change pgtable_t as 'struct ptdesc *' in other archs. That could >> simplify and clarify related code too, isn't it? > > Not sure. s390 and friends squeeze multiple actual page tables into a > single page and that single page has a single ptdesc. > > I was rather hoping that we can make the code more consistent by making > everybody just point at the start of the page table? (that is, make it > consistent for all, not use ptdesc for some and pte_t * for others) > Got it. That would be great if owners of these archs like to work on this. Thanks Alex