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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6c184ce9034sm10939096d6.73.2024.08.26.07.34.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Aug 2024 07:34:42 -0700 (PDT) Date: Mon, 26 Aug 2024 10:34:39 -0400 From: Peter Xu To: LEROY Christophe Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Vlastimil Babka , David Hildenbrand , Oscar Salvador , "linux-s390@vger.kernel.org" , Andrew Morton , Matthew Wilcox , Dan Williams , Michal Hocko , "linux-riscv@lists.infradead.org" , "sparclinux@vger.kernel.org" , Alex Williamson , Jason Gunthorpe , "x86@kernel.org" , Alistair Popple , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" , Ryan Roberts , Hugh Dickins , Axel Rasmussen Subject: Re: [PATCH RFC 2/6] mm: PGTABLE_HAS_P[MU]D_LEAVES config options Message-ID: References: <20240717220219.3743374-1-peterx@redhat.com> <20240717220219.3743374-3-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Stat-Signature: 7puf1ptirwbyof7wdnjmdg1dkfzi43ei X-Rspamd-Queue-Id: 85C5C1C0016 X-Rspamd-Server: rspam11 X-HE-Tag: 1724682886-621550 X-HE-Meta: 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 pZS4sFCT s32o43YdT3jzqO/vRToMl6hac2nnXoh06nRfjcglo45cHGLHfvSTxB3lj+oLoP7y40zSVCwS/I7/nlVhOagaZG/kIVWFhXHp8psDkwqlox7Sj49qK16MAqyc1S8/KJRP9P+/A9ISq8TVWb0pEzsev09jltgmBfihKYhHD8Q5scYzfq/alNYq01cSALIv8Md0tpqoj61oXqfiEw/V/iYSmWe1pL+K/rbExm5xO9PIq/8p+0B1I9nEXtNBqNoi2q+ljQvNCrY5Ls1Nq731ghQAQOg3beBnTjlXLdd3b1rgrdBiONmGiGJ0dsyn7v+AkWIf1QKasonWc6S0h30loZkvtLz9mdG9E9pnOYEKobjQZGxc8djq59XOPT2el42pNJq4JX8OWPF62RiuYblU= 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 Fri, Aug 23, 2024 at 06:19:52AM +0000, LEROY Christophe wrote: > Why is an option needed for that ? If pmd_leaf() returns always false, > it means the arch doesn't support pmd mappings and if properly used all > related code should fold away without a config option, shouldn't it ? It's not always easy to leverage an "if" clause there, IIUC. Take the case of when a driver wants to inject a pmd pfnmap, we may want something like: if (pmd_leaf_supported()) inject_pmd_leaf(&pmd); We don't have a pmd entry to reference at the point of pmd_leaf_supported() when making the decision. Thanks, -- Peter Xu