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b=PGEAs34F6BiEJMajWABVfRAt6apO6GdmemXHMH9ZaDCtfTlhEYqpEiVDB/HATlSB+ 5c8IZjhNSJbfvIKg3U/WcQ8QMFrETr1FwWAEiMnEo3zeh1Eu0mWa/S9jPYpERLx66T 2BjXib8XHNbQc7T3GRgH4fqDla3faZEtb42/ywbV8Pbb6efs2PGh/vIfIJmL1bdHNM CViMGplX75QLZCOIlfNt9NbEG9KrbTjrWe/WC5MAibT4lN+1YOTGS59HzxKPT3ENFH pf7bxdmXswR3mZijG+ATccnjAev3cNuDR0uzCu0H9xumEJMiUdcPjwBYm8fm8JsOvm cdF0DYB088P2w== Date: Wed, 17 Jun 2026 21:40:25 +0300 From: Mike Rapoport To: Adrian =?utf-8?Q?Barna=C5=9B?= Cc: Brendan Jackman , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, Catalin Marinas , Will Deacon , Ryan Roberts , David Hildenbrand , Ard Biesheuvel , Christoph Lameter , Yang Shi , Brendan Jackman , owner-linux-mm@kvack.org Subject: Re: [RFC PATCH 3/6] arm64: mm: fix restoring linear map permissions on execmem cache clean Message-ID: References: <20260611130144.1385343-1-abarnas@google.com> <20260611130144.1385343-4-abarnas@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 41F4FC000F X-Rspam-User: X-Stat-Signature: 5afpyqzbjurgneysof4cahwrmszqzabd X-Rspamd-Server: rspam08 X-HE-Tag: 1781721634-109819 X-HE-Meta: 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 HUPboWuo kUZIzuPoWJfPggw7wZYlxDgZxL4W5t3e/GT2b+z8l+eARwscLaoaRr4/LuXv4r4TlpXPZaLg+kIL50z3pSuLSrRKuN9fBH1W8JfJb8zAs76RYI0EjvaZC0UZHGVwW4qBFPDf4IeZgxBZ3jzGKo0zPg4PlIXJSx/sHWoceiEcfRKuXcxAWhIFIwaj7nat5cI/u7QA4dYZomh4umBVfMKCok49BxuY6SdQ4lmFEnd/BFM/+hb7XWyy2puQcWq9a0HkyW/cMFBIroiyBMvLtmuqMGk0yQmHCCkpJ+1NhRg7LVoziEz3fOlB/9d7WbvtISr79+8VzLAP3bRAWJt4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Adrian, On Wed, Jun 17, 2026 at 03:18:27PM +0000, Adrian Barnaś wrote: > On Fri, Jun 12, 2026 at 10:17:55AM +0300, Mike Rapoport wrote: > > > > > > Hm, maybe desirable for execmem but that doesn't really mean the x86 > > > behaviour is correct. Maybe it makes more sense to change the x86 > > > to align with the arm64 behaviour here? > > > > > > BTW we should probably document this API a little bit, I never thought > > > abut what "valid" actually means until now. I had thought of it as "I > > > can access this memory" but that's an unclear concept and now I realise > > > "valid" is a technical concept in Arm that's confusing. And it's extra > > > confusing if the kernel API uses "valid" to mean a _different_ thing. > > > > I've got confused too and that's how set_direct_map_valid() got into x86 > > with a different semantics than on arm64. > > > > What execmem really needs is set_direct_map_default() variant that gets > > nr_pages. > > > > AFAIR, set_direct_map_default() has a single 'page' parameter because it > > was added to reset permissions for the direct map alias for vmalloc()'ed > > pages before there was VMALLOC_HUGE and each page had to be reset > > independently anyway. > > > > Maybe it's time to add nr_pages to set_direct_map_valid(). > > I was also quite confused by this initially. I spent some time debugging > until I realized why unloading all the modules was causing the kernel to > crash. > > The reason I took this approach was that I wanted to send out a working > prototype for arm64 that wouldn't interfere with the existing, working > implementation on x86. > > Following your suggestion, I can put together a preparatory patch series to > refactor the set_direct_map_* APIs to accept a nr_pages parameter. This There was a patch Nikita sent a while ago that does something similar: https://lore.kernel.org/all/20260410151746.61150-2-kalyazin@amazon.com I believe you can start from there. > refactoring would also allow us to drop the redundant set_area_direct_map We can't drop set_area_direct_map() because vmalloc pages might be not physically contiguous. > helper. I could then rebase the rox_cache series on top of that. > > Does this sound like a good path forward? > > Thanks, > Adrian -- Sincerely yours, Mike.