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AJvYcCVSLjMeHrO8CZYkWL3xW2kcUjFoUK7b7nOGKFfxxP+tpdurcfqK+BdKDRjFWCIeLIywldWiWJB7ag==@kvack.org X-Gm-Message-State: AOJu0YyOYheoCpGIvnUSTUFFSmM4JA0N0l00B+VyYGVumOFM0UxY27yw zRyQ49eAB05EbqFuMDVXOy1OsXompnqoC0BxaD6y1f8BNNYH2/ayEHOk+1Yka23QkIa1dCl3Riv Am/ejfwmFAkgh9Ba57sf48LuFC0c= X-Gm-Gg: ASbGnctgRqJPsrvsjssidK6V2lErJxd4gGipEiNwf/xYs4pXfn3AA0HpfWCyuea+eJI E6yndKALKQ9nHTWW9i0mvfxI2kUyGKyrroR6ZimMFT8zYcJkwFRskX3bYvnqgrJUmk28wZwIVSi rGHu9Wl+z3SvrU2c0ViHkhkSxEOVqX X-Google-Smtp-Source: AGHT+IH1yYjBDq+fpIs2910Udi8BvvFKAuL4iL47+8Y/BbUeB+wz+UXTXrj23xSjcuh9pdg/bHLlXJsGj0VslDrI/G8= X-Received: by 2002:a05:6830:3497:b0:71e:4fc:6ee1 with SMTP id 46e09a7af769-726e79e202cmr1547852a34.9.1739261138277; Tue, 11 Feb 2025 00:05:38 -0800 (PST) MIME-Version: 1.0 References: <20241113095833.1805746-1-zhangchunyan@iscas.ac.cn> <20241113095833.1805746-2-zhangchunyan@iscas.ac.cn> <87frl0snf6.fsf@all.your.base.are.belong.to.us> In-Reply-To: From: Chunyan Zhang Date: Tue, 11 Feb 2025 16:05:02 +0800 X-Gm-Features: AWEUYZmR3vcC-5RUc00Y8UvIfNPJCSy9ifpTouB9LReWy6id2n5cEvTpBNFA-9k Message-ID: Subject: Re: [PATCH V5 1/3] riscv: mm: Prepare for reusing PTE RSW bit(9) To: Deepak Gupta Cc: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Chunyan Zhang , Palmer Dabbelt , Albert Ou , Paul Walmsley , Alexandre Ghiti , Andrew Morton , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Alistair Popple , linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: B3EB91C0019 X-Rspamd-Server: rspam12 X-Stat-Signature: nsiqa587ice6c6x1fdgg3g4mtbbrgddh X-HE-Tag: 1739261139-527098 X-HE-Meta: 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 /609K+R+ 21T5+JaRZX81izDNlCX/sZSBelPfvFif9sLGRAzFVjV7x1t32ei8yoyFKx5BVz7/f99+XE/8qoXaRD113DlqDeCarzckldrgX+v9wQKPE4CLZSRtcy35OJOq/n5uoeMJZGahJWX1Sqx8OII9Nz5HP/9iNfkCharI8EEKWJ9KW8Vv7PF+1Y89MppwH37Xai8uL7q1kRNjiggv6rOrKAwPqwkOSgxUQvDZdeXI9VMzrBAmtQ98YVYSXwwEmiQov8w0+UDuJvpF+pHeO6kTvnDcCGUR7ZxFSmOxOHN+yA2Lfj4+EupKUKdrGtJWxI0mBJffyw2rUk2wFIlTMFyKKIfl9VTTSwj88LoJd0f6+n6iHSaVRV6YF7gco6CnDWvqIGo/Qfcy1M7xHqOessbKZXUqasC+Lj8JgaXZMMQIztz/l29KECnzzX6neDcO2+A== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000690, 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, 11 Feb 2025 at 12:01, Deepak Gupta wrote: > > On Tue, Feb 11, 2025 at 09:20:22AM +0800, Chunyan Zhang wrote: > >On Thu, 30 Jan 2025 at 16:42, Bj=C3=B6rn T=C3=B6pel w= rote: > >> > >> Chunyan Zhang writes: > >> > >> > The PTE bit(9) on RISC-V is reserved for software, it is used by dev= map > >> > now which has to be disabled if we want to use bit(9) for other feat= ures, > >> > since there's no more free PTE bit on RISC-V now. > >> > > >> > So to make ARCH_HAS_PTE_DEVMAP selectable, this patch uses it as > >> > the build condition of devmap definitions. > >> > >> Heads-up: It seems like Alistair's series [1] that removes the devmap > >> PTE bit will most likely land in 6.15. > > > >Yes, I've been keeping an eye on Alistair's series, intended to update > >this patchset after Alistair's patch that removes the devmap PTE bit > >got merged. > > Please keep in mind that even after claiming back devmap PTE SW bit, a co= mpile > time decision to select between uffd-wp and soft-dirty is not desirable. Yes, I agree. I've read your aother email. I also hope we can have more RSW bits to use. So should we add uffd-wp and soft-dirty support on RISC-V until we have two RSW bits for these two functions? Is an undesirable solution better than no solution for now? I can optimize the code when we have more free RSW bits, that's not hard. Thanks, Chunyan