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t=1789763527; bh=X2Gm2LzEC02MoKL1Mljhg5EEmo7yk0sahCQ3OG9Pwz0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=KBuVz8ZppMXav6gtxngSrOjWg+cF99Z7MBSk5hZD/eNMNv37m4Oqg7kfD7P5V/ljy Pzyry1gNHcyH4f8LHNo1gxbE3w7rL/pKRnFLuUPa8kkRF0xUteAO14sQVLMPeUdcLg LW8Kt3C8cX+5rN/zA1nlc5YjMtRJouLe2p0Tt7OGTgi8K465aQ5ITyz3a12In4F/1s 3q7+w3WpnNtzWgmkVzV1HqZadxWxZ++UjYP203B+CEZxsQqimj6TnIsO4Lp/4mlrxn BjN2Fbv8Y9OjiW2P3RnDF6PDai56BIsYfIwhIGiUnt/jhV5X6j3gtNKIueVdycQ54W M5n+aRYMsCsqw== Message-ID: Date: Fri, 18 Sep 2026 22:32:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/huge_memory: disallow raw PMD mappings of the huge zero page To: Kiryl Shutsemau Cc: Lance Yang , akpm@linux-foundation.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260917121010.60966-1-lance.yang@linux.dev> <8c70259a-94ed-415c-89c1-572145c64670@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0CD20A0004 X-Stat-Signature: g9w3db3ds8d7opynob8z477jy7mp4mdp X-HE-Tag: 1789763528-125030 X-HE-Meta: U2FsdGVkX18g/UblLXrdCXcIAfuatQehABZvNEKB+aFnUU0cbaxOqf4WhtlXFRxrPUXn3vYekphNEGuEcFkkgO+O/Byld5J+yF0c3OBjMTsXiPUnXvVkRB3VAU50hAguDBzPR+wCahZh9LIuLiWVLFHjTZfIJ1N4YXNFc5XKTlYozci1J3iYZy2/E5oGGBzJCdKovbaA/kAgvGeizEBlPaPvOKXD3hWQjG7UzuNitsMHJyuHlqpyhX2/oBIm/7LvunFMT7zOKr7IbMw7hgmxH6m0nLyyCfe0EKxcC8zehUd8GmDwaUcu0R1UBxzt16yPovq17xh+Btor5uHfS6dOQU+FxG9N6SWLAGhWRo2wkRWhdNWNuvMIrDZE1cHU4iEbCCUNUbdP8DTJu8RH/51cSmO4JbljCH1Qb/PNl1oWLJ7kcVs9soRfiJ8hdjbI/AWgc/lPVJqrAPmWQAjXfDdaIoQFIFvY2qvT5fkgqXlQs71YJjRcX2+9+xJnesmYSVxG+/d7pAOkqKdT15qaRCzWRAushO28R0ADESPTIXwuaZmxn2aiGVCaq7WfY6SYjwb8PifDxyZGYeLmTJEsy+jpx45Z5Tcsuopid6gSo9I/fXlZtx8xAZuvZb1QhpiWgIwsU2SLhmScr08qD4422i3qXZkE8tCXNU7Vo1FRXMENNAQag1Yr1xxQbvTgonqBx+5XgexUq9ZAsITuaHK9BDB4hOJ7d3aqIIjOoc4fMB85k0R+csy44fKHYSl6BIje1+9jMb8NS60Kp5tAA7jqCaCKuVSK/WiutaFxcVky37Hk2g5afkrgccVAxOc+Jmexlweberbzsms9fzdhZjHvIU/PwenEv+LjTZKqGx/LnQdtesAKfoffhligVgfBj7ZAznBA8BKl0BuaKAIykZ8bC/KdNCjhLW6PXZIXfg22kibZnV6HCbUPLWPvovjqSbhlxf5rl5iSZlhf//QJNtpHn84 YloskYcb lc7+5mqAId4y1MNpyvf2n/ymMVjnNlu0bxzc1bqknm/1/m5nvqfUvnfW9UF1enXClVZ8DWn0xgIjkezgAH8H4CapWBI9MjIjtWVO9ZTknzS4JLjv1FFR61d93GaIKFZB4qk9KL1fsZJRFRtm/y1Sq++vQX5d4EVTT6EBmOkUqgvXYEhjhn/wp/MsYpI4uSfexBo548tbukfVM7TPl2X3j8APJwkYurqetJp7D9Cg30cTLfUQ4hsEpE7NTFCj8lSEkUNq2nBrE8uHOrYyx1VfmMhCjs8xHXDrHWUkZmTiF8FqT/UmbUlhbEKUb5Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/17/26 18:03, Kiryl Shutsemau wrote: > On Thu, Sep 17, 2026 at 05:29:48PM +0200, David Hildenbrand (Arm) wrote: >> On 9/17/26 16:32, Kiryl Shutsemau wrote: >>> >>> The patch looks fine, but don't we want to cover the same for non-huge >>> zero page in vmf_insert_pfn_prot()? >> >> Why would the zeropage be a problem in PFNMAP mapping? > > Nothing enforces that it is read-only. Well, ok, that at least would be easy to check. There are other reasons why we'd want to disallow it ... similar to the check in vm_mixed_ok(). Which reminds me that we should try getting rid of vmf_insert_mixed() at some point ... but it's tricky. -- Cheers, David