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b=EceVUvxL1OnZids3GRqeq1btRudotGLxGnTzu4CsVMZohND9PtMu9iepxejI6Lc4e lCb+8Gpj01vLylCaE8zNKBJpXIXHsq8qJkTbTCuptNXWEyA7zDptDe1LKby7gYWd+U 5pNOxKOAOcEGtsuqqVSOGWGRKrlDwlSrlfvaAfWUMg+Df399cbWJPxKeiRU9M6em+3 YT4JnocZn3WzwtlbylfValFVt7mnMvqooGXe7CuDLeahKeCebD01bLSFFfhq+la3dv nkl6EQigdTw4PjDi+Wp+Pdd5BkI5DtlSMnt+fUDuONmDt2aat+HgAm3JXLIi4ChCp5 X7T1w9wWUe4eA== Date: Wed, 28 Oct 2026 19:08:50 +0200 From: Mike Rapoport To: Vincent Donnefort Cc: catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, sudeep.holla@kernel.org, jenswi@kernel.org, robh@kernel.org, mark.rutland@arm.com, sumit.garg@kernel.org, ardb@kernel.org, thierry.reding@kernel.org, david@kernel.org, danielmentz@google.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, op-tee@lists.trustedfirmware.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/8] memblock: Introduce MEMBLOCK_PTEMAP Message-ID: References: <20260921110050.3977591-1-vdonnefort@google.com> <20260921110050.3977591-2-vdonnefort@google.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260921110050.3977591-2-vdonnefort@google.com> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 02845100004 X-Stat-Signature: wkcsa1e48kiqa3uphd55zx7z3ibaezia X-Rspam-User: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793207340-286038 X-HE-Meta: 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 UPvjB+BW 1evr4rJsmoMVg6R279W+1z1NkdiGQiArP2eFWFFTsDw9/KjxR8MjQwMVIxgeJIN3kTMpLjLGLvJiTStgQWcra513wA29j1wEAraW+u9bqhjGTOBODS0DguPCyAk2QhKMWtBmtAaIoL4tG0bB+cbhJHnqepOb+wKh/LoqsNa4bKL1BhacS6pUSAI4qJo8i4SmtlApDMdVRxb2H88lck4hNcihgsa8t0UFLGcnJIuw42LWoorB3JnI8j+Ze9vbA7jJ9a0dbHb2iRWm52EfJWTgVIsSJ9Dfg7+xExH70onjFsCvvFIWcUqX5jHKdGqEyJsaD5VYR8p2+1oTZH9w= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Sep 21, 2026 at 12:00:43PM +0100, Vincent Donnefort wrote: > Keeping PTE-level mappings is interesting on some architectures as it > allows mapping/unmapping pages from the kernel direct map without the > risk of splitting blocks which, under the break-before-make rule, may > trigger page-faults the kernel can't handle. Let's be honest, it's arm64 :) I believe that some powerpc variants could use this too, but they don't have break-before-make, so either "some architectures" or "break-before-make" should be rephrased. > However, mapping the entire direct map at PTE-level is costly. So > instead, create a new memblock flag MEMBLOCK_PTEMAP to selectively apply > a PTE-level mapping. > > Signed-off-by: Vincent Donnefort > --- > include/linux/memblock.h | 18 ++++++++++++++++++ > mm/memblock.c | 30 ++++++++++++++++++++++++++++++ > 2 files changed, 48 insertions(+) > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index aa845f488327..13263055996d 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h ... > @@ -285,8 +289,16 @@ static inline bool memblock_is_mirror(struct memblock_region *m) > return m->flags & MEMBLOCK_MIRROR; > } > > +static inline void memblock_warn_invalid_map_flags(struct memblock_region *m) > +{ > + enum memblock_flags map_flags = MEMBLOCK_NOMAP | MEMBLOCK_PTEMAP; > + > + WARN_ON_ONCE((m->flags & map_flags) == map_flags); > +} > + > static inline bool memblock_is_nomap(struct memblock_region *m) > { > + memblock_warn_invalid_map_flags(m); I think it's better to check and warn when setting an incompatible flag rather than when querying it. > return m->flags & MEMBLOCK_NOMAP; > } -- Sincerely yours, Mike.