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Tue, 11 Jun 2024 16:10:28 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id O1RtKvR2aGZ3bgAAD6G6ig (envelope-from ); Tue, 11 Jun 2024 16:10:28 +0000 Date: Tue, 11 Jun 2024 18:10:27 +0200 From: Oscar Salvador To: Peter Xu Cc: Christophe Leroy , Andrew Morton , Jason Gunthorpe , Michael Ellerman , Nicholas Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v5 02/18] mm: Define __pte_leaf_size() to also take a PMD entry Message-ID: References: <172b11c93e0de7a84937af2da9f80bd17c56b8c9.1717955558.git.christophe.leroy@csgroup.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: CE88F40011 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: 5jufkbuwec6ay95he3jd5x1456hd9bp5 X-HE-Tag: 1718122230-73676 X-HE-Meta: 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 239RD4iL 9Y9lzBaotiyb/xizIbt8y9aHyEzNw5Xn9G+8dqeNuQBOHkKF+l3UUESRmeeHfi2q0ui8GJPSDFF2BTeZ9vSO2BDlaKhRLU2l5XPtm59tl1n9ebIphl0oLCEPuCb3U0hdmHE2Dbf64cKWgcbNntTCnaTNCr/0ZjQzWuka4tHYBvaD/IZGcM8fl104UhgdcCeta2ErSHvjIkH+m0aChTf03VBHaKh5EVlNQGXlxAIwfULQOwgP8EMWCAsQWdQ== 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 Tue, Jun 11, 2024 at 11:20:01AM -0400, Peter Xu wrote: > On Tue, Jun 11, 2024 at 05:08:45PM +0200, Oscar Salvador wrote: > > The problem is that we do not have spare bits for 8xx to mark these ptes > > as cont-ptes or mark them pte as 8MB, so I do not see a clear path on how > > we could remove huge_ptep_get for 8xx. > > Right, I remember I thought about this too when I initially looked at one > previous version of the series, I didn't come up yet with a good solution, > but I guess we probably need to get rid of hugepd first anyway. We may > somehow still need to identify this is a 8M large leaf, and I guess this is > again the only special case where contpte can go over >1 pmds. Yes, we definitely need first to get rid of hugepd, which is a huge step, and one step closer to our goal, but at some point we will have to see what can we do about 8MB cont-ptes for 8xx and how to mark them, so ptep_get can work the same way as e.g: arm64 (ptep_get->contpte_ptep_get). @Christophe: Can you think of a way to flag those ptes? (e.g: a combination of bits etc) > I'll leave this to Christophe, but IIUC thp is only PMD_ORDER sized, so > shouldn't apply to the 8MB pages. That might be it, yes. -- Oscar Salvador SUSE Labs