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Wed, 28 Oct 2026 17:09:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C17901F01828; Wed, 28 Oct 2026 17:08:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793207340; bh=mzc7Hanv0CDK4THhGHtewy5AYoBUPo6jlbuGdSqeuHA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; 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 To: Vincent Donnefort 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-Action: no action X-Spamd-Result: default: False [-9.00 / 15.00]; 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no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-op-tee.lists.trustedfirmware.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header 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 X-Mailman-Version: 3.3.5 Precedence: list List-Id: Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: From: Mike Rapoport via OP-TEE Reply-To: Mike Rapoport X-Spam-Status: No, score=-16.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 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.