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Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/secretmem: disable under HIGHMEM Message-ID: References: <503aee9e-97fc-4889-a379-3c0a5d140554@kernel.org> <7e7f20de-c43d-40f7-82d3-8d05ceb3656b@kernel.org> <21e7746b-9bc2-4643-b0ca-c59e0c77f810@kernel.org> <5653474e-6692-4353-b5d6-e57b6ab76eaf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5653474e-6692-4353-b5d6-e57b6ab76eaf@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 85A874000C X-Stat-Signature: i7o7cjf7ogji8rx8kinuh4jnoz7zjstg X-HE-Tag: 1784199135-430401 X-HE-Meta: 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 H/+KoqOD BVJO6dLeHv8VuCMvfySeAbfYgh1FN+UI9b1Vzma47Pw2IyUMEDgo9u+ZVSaB4iY5A3KvrkLNVHcvXFr24PNz5lVZnuCOsTbHH+Wwyk54lyf/KrttqwbezSzOgqSJnCsJ0eeN97Isci31G8T3Tdz4AYQcyP4YwPagGdCTAKc4c2iTClyebVhO0wZBSUBsg6P5JlWIYIl6h4h1GnCdpSqFmowd3l1QscgrNVAmSpcirFijM/x7WHxo4dwmM9UgcL5MnRHmO Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 16, 2026 at 12:08:07PM +0200, David Hildenbrand (Arm) wrote: > On 7/15/26 16:58, Mike Rapoport wrote: > > On Wed, Jul 15, 2026 at 03:49:39PM +0200, David Hildenbrand (Arm) wrote: > >> On 7/15/26 15:44, Mike Rapoport wrote: > >>> > >>> No, I mean what Brendan's patch did: > >>> > >>> config SECRETMEM > >>> default y > >>> bool "Enable memfd_secret() system call" if EXPERT > >>> - depends on ARCH_HAS_SET_DIRECT_MAP > >>> + depends on ARCH_HAS_SET_DIRECT_MAP && !HIGHMEM > >>> > >>> We can change gfp_mask as well for the sake of pedancy > >> > >> Why not change the gfp mask only then? > > > > Citing myself from a few emails back: > > > >>> But still with kmap() and friends not being an NOP the promise "kernel does > >>> not map this memory" does not hold. > > So you're saying that kmap() would perform a mapping for a non-highmem page? > > static inline void *kmap(struct page *page) > { > void *addr; > > might_sleep(); > if (!PageHighMem(page)) > addr = page_address(page); > else > addr = kmap_high(page); > kmap_flush_tlb((unsigned long)addr); > return addr; > } > > I'm missing something important. Yeah, you are right, GFP_USER should do. > -- > Cheers, > > David -- Sincerely yours, Mike.