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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JRoxl9E+QrX+IO3atrSghjI9x/qg48SBeUoB1iHXHkCx7rak+q7DUoHyAtcB2PWYV hmycgMaqDchkjeaR2c2OvTp7h462MRv11iGZ4k/gz8RFYH0JjEvEaYuMwxBYfLXZdP a/vAsnGfvbfQ8np3IkFUOQE1xCeEA50NtIZsQ9qE= Message-ID: <66270f42-931f-4043-b24c-edcc4cad74b8@arm.com> Date: Thu, 3 Sep 2026 18:41:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v9 02/25] set_memory: Introduce set_memory_pkey() stub To: Linu Cherian Cc: linux-hardening@vger.kernel.org, Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , "David Hildenbrand (Arm)" , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , =?UTF-8?Q?Pierre-Cl=C3=A9ment_Tosi?= , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Ira Weiny , Lorenzo Stoakes , Thomas Gleixner References: <20260818-kpkeys-v9-0-743ad31b2c8f@arm.com> <20260818-kpkeys-v9-2-743ad31b2c8f@arm.com> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 44rz8nip7o1ccmpnnbxcprs5og81gipu X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0499E40004 X-Rspam-User: X-HE-Tag: 1788453703-88848 X-HE-Meta: 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 P5hHe3/2 /7nco76/JGPIDa9X7fpJhxU29kiqAWhzdY+BhdNDIJuc+nCG4+kg7B80W1VlvQXyA3K2rzUaLEvlwzQZi9oGb2KsH+LoAPGvgtASwi9X4lc3WQ84oOBGbVugLUhvWfSDaD55AQGL3bbFrt/j+HQAU/8dkSwMudejzzSpLXD8MTZpdE1j1lsXph1Y456oq/EpLbVuK+QoOqffmwbIMdg9CGHzr+2CIamlecbWGbDSpxwKFSXp1GOo6bxvDQTEu8YpjrrnhXekVQjrhr4DiM5dC01NPMOy8Up5YfFaWbFydahbZMkZMsvDsKibF/5+JvDwLbnm9ArSFD6sATGGVyy0SwTrSzA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 01/09/2026 16:33, Linu Cherian wrote: > Kevin, > > On Tue, Aug 18, 2026 at 03:08:44PM +0100, Kevin Brodsky wrote: >> Introduce a new function, set_memory_pkey(), which sets the >> protection key (pkey) of pages in the specified linear mapping >> range. Architectures implementing kernel pkeys (kpkeys) must >> provide a suitable implementation; an empty stub is added as > Could you make it explicit here why we are restricting this only > to the linear mapping range ? Would be helpful to add the reasoning > in the commit message and as comments. > > Essentially we are also making a assumption here that there are no > aliases to the linear map ? We're not assuming this, this function is called on pages that are also mapped as part of the kernel image. But indeed it ignores aliases, unlike e.g. set_memory_ro(). Really its name is wrong as discussed below. >> fallback. >> >> Signed-off-by: Kevin Brodsky >> --- >> include/linux/set_memory.h | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h >> index 3030d9245f5a..7b3a8bfde3c6 100644 >> --- a/include/linux/set_memory.h >> +++ b/include/linux/set_memory.h >> @@ -84,4 +84,11 @@ static inline int set_memory_decrypted(unsigned long addr, int numpages) >> } >> #endif /* CONFIG_ARCH_HAS_MEM_ENCRYPT */ >> >> +#ifndef CONFIG_ARCH_HAS_KPKEYS >> +static inline int set_memory_pkey(unsigned long addr, int numpages, int pkey) >> +{ >> + return 0; >> +} >> +#endif > Would be better to make this (linar map range)constraint on the API name or that passed > as a boolean flag ? Indeed, in fact I've been thinking about renaming this function for a while and I've already done it locally :) It'll be set_direct_map_pkey() in the next version. > Also, it would be better to have the __is_lm_address checks in this generic wrapper which > then calls arch_set_memory_pkey ? That's not unreasonable, but such pattern isn't used by other functions in set_memory.h and I'd rather not deviate too much without a good reason. - Kevin