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[77.7.17.232]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-484492cf550sm7547096f8f.37.2026.09.02.10.08.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Sep 2026 10:08:53 -0700 (PDT) Date: Wed, 2 Sep 2026 19:06:56 +0200 From: Karl Mehltretter To: Dev Jain Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, Anshuman Khandual , Ryan Roberts , Mark Rutland , Andrew Morton , Muchun Song , Oscar Salvador , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: hugetlb: fix BBM for mprotect() on contiguous PTEs Message-ID: References: <20260901131823.15799-1-kmehltretter@gmail.com> <551663b9-d031-4755-af7f-dc6c22524b35@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <551663b9-d031-4755-af7f-dc6c22524b35@arm.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 83FB1A0006 X-Stat-Signature: tckra4sunr3nmgdjs1q86b7thmsu1fx6 X-HE-Tag: 1788368935-210673 X-HE-Meta: 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 iPb4g1y6 KF2cDisQVNeSld0JFg7/vbEa4nsREqJZQEqeAppvA1f/P4cVbCCVyW4dBzBepZvgsj+y/IQU8VHMBb8817s4WdHpmtNG1MWU51W8iqV9rsNk9ditDAk+YI7Zw3y8fUist9KxwkfQwNA8/cB11Szz1pD89BnFd99jJCt54sPqwr+yZJiAe7Q0Z9lZ1hGQ4B4mQsNnp4GH3x6AGw9c4/xD2/8i8Qu5/MOrxZDGgO7yJTF9ethSDZNoj5JKrVRV1pK3aXWAdwcgD9KgfPs4PmLpryUhG7CzXP40NK25NnM4pcpSLRTO3TrZcRvvF0izIb8wB3RTRl5i6mhzkvEzd4lZcWo9Y64E3bebRlxs3HmFw98hc6OM8FUyLzgFlvubxmhdpN6dPvtR2quJd6iE46nmgHBoT6xi7+RUkK7Ltbdv0shhntqL4A3AP3Q2mRw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 02, 2026 at 08:16:36PM +0100, Dev Jain wrote: > Upon discussing with Ryan I got to know, he was implementing the > contpte stuff for non-hugetlb user mappings and that basically > drove a clarification on the semantics of contiguous bit and > this rule was added. > > If you see currently for non-hugetlb mprotect() we do not flush > during contpte teardown. > > So if the above reasoning makes sense, I can infact audit and > remove the flushes in the hugetlb helpers. > Well, that's quite a turn of events! I wasn't aware of R_JQQTC or the architectural clarification behind contpte_wrprotect_ptes(). My QEMU checker was based on the older assumption in commit 410982303772 and the existing hugetlb comments, so it treated a clear and remake without an intermediate TLBI as a violation. So... Please consider this patch withdrawn. It's good that this may have uncovered an opportunity to remove the flushes in the hugetlb helpers. Thanks, Karl