From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9DF08395AE1; Mon, 1 Jun 2026 10:09:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780308574; cv=none; b=jkWQknyAM+s13NAeeCvkOyK7TCO1+rDHBzIezB9Gxin146dEDN0i4M76j1cmMBasLcZ02DaQ0cVZ/Pc8exEK++E/wEaop2lNsbiKYO8AJee0F+1YIFHfuFpS+eC4v/JhFcvcTRmKOINOjeL07OMm0yvUQ1XgmwPoTo/lkzACoQg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780308574; c=relaxed/simple; bh=+2MB96/BVouH0+TPLKMKehOeyNIGPTacG9p6OCNjZIE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lXm5sM5cnrgmQ12DQUnUWTVvfFKL8JfuAVkXG38yaxdnqcHNwZfZbzZfYOUGfikI5cvcBLkaQpJ0dafMyEQAczOmGljm/q0hfQvAoeRvHOcgNW9vd0uLitGoxpWv+OhzNAqmY+vW2Mf6tFxrsmgzTvWM2LZoYALZKcQq+9HZLF4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E/RSr7+q; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="E/RSr7+q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C9011F00893; Mon, 1 Jun 2026 10:09:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780308567; bh=telDdSC7/EI4bm0my2SYNWvjV6/+1WMfaGUydwsM0JE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=E/RSr7+q/6nIFb+9C6c9jmKbP1es072hXYz1IQTGwUjqaPxnQ3p0yc/KbCu5ZwWW7 O4de5CsFCu+YBhZn0/qvFCVmXnhQZ+9bcoLMBeKqREXxlFIr5oU6mXmOrcX6VruVjp j5WG8L1x8M48jYN/AQiG6LpMUDMP96kfuQ5pbitNPPhKrhMEkpVqoLAjig4X1ATvh5 l1DeuNTi+4uytvO3r+WRDidfs8pVNImknpTmQZ48FHAhfLQgEP5r/X2x3TH3Ibx3rF WW0u5PA4rvSr7OS8rrXPbpZCp0JRJt7WiTn0MRU8VhZ3ldi28u+HEvu6N0aoZFitOS ihVHv9tWG1ZZw== Message-ID: Date: Mon, 1 Jun 2026 12:09:13 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v18 06/14] mm/khugepaged: generalize collapse_huge_page for mTHP collapse To: Lance Yang Cc: npache@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, liam@infradead.org, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com, usama.arif@linux.dev References: <2024af56-5e99-4799-a586-e9ba756cecb9@kernel.org> <20260601032804.96122-1-lance.yang@linux.dev> <1c99294c-9ebe-4856-bfde-09801701d75c@kernel.org> <32751424-8ad3-4fd2-9f07-8a4f5a98d632@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/1/26 10:44, Lance Yang wrote: > > > On 2026/6/1 16:15, David Hildenbrand (Arm) wrote: >> On 6/1/26 09:49, Lance Yang wrote: >>> >>> >>> >>> I had Codex do the boring grep-work through the arch update_mmu_cache* >>> code :D >>> >>> MIPS doesn't seem to be the only code doing a re-walk, but it is the >>> only one I found that appears to assume the PMD/PTE walk cannot fail, >>> without checking whether the PMD is none ... >> >> Okay, but likely the other code that tries to handle it is also problematic. >> >> Best to make sure the page table is already installed when updating the entries. > > Neat, makes sense to me :D > > That way the page talbe is back in place before any arch hook gets to look at it :) Right. I don't think we could run into a deadlock here (nobody should concurrently take a look at the page tables in the first place). Not sure about the memory barrier I dropped: the page tables are already properly set up (just some entries cleared), so I'd assume that barrier might not be required. -- Cheers, David