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X-CSE-ConnectionGUID: 6yd8/aAnRrq/j6ABBwrs1g== X-CSE-MsgGUID: lBpy6vZ+TLi1w9U7ElUdJw== X-IronPort-AV: E=McAfee;i="6800,10657,11518"; a="61016765" X-IronPort-AV: E=Sophos;i="6.17,278,1747724400"; d="scan'208";a="61016765" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Aug 2025 06:55:54 -0700 X-CSE-ConnectionGUID: C08Q9FYCSM6nVurQEU1rUA== X-CSE-MsgGUID: 0UUoKXwIQdqEQIhB8E5XDQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.17,278,1747724400"; d="scan'208";a="196765115" Received: from dwesterg-mobl1.amr.corp.intel.com (HELO [10.125.111.51]) ([10.125.111.51]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Aug 2025 06:55:53 -0700 Message-ID: <83c47939-7366-4b97-9368-02d432ddc24a@intel.com> Date: Mon, 11 Aug 2025 06:55:52 -0700 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/1] iommu/sva: Invalidate KVA range on kernel TLB flush To: Uladzislau Rezki , Ethan Zhao , Baolu Lu Cc: Jason Gunthorpe , Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , Jann Horn , Vasant Hegde , Alistair Popple , Peter Zijlstra , Jean-Philippe Brucker , Andy Lutomirski , Yi Lai , iommu@lists.linux.dev, security@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20250806052505.3113108-1-baolu.lu@linux.intel.com> <20250806155223.GV184255@nvidia.com> <20250806160904.GX184255@nvidia.com> <62d21545-9e75-41e3-89a3-f21dda15bf16@intel.com> <4a8df0e8-bd5a-44e4-acce-46ba75594846@linux.intel.com> <4ce79c80-1fc8-4684-920a-c8d82c4c3dc8@intel.com> <2611981e-3678-4619-b2ab-d9daace5a68a@gmail.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 8/11/25 02:15, Uladzislau Rezki wrote: >> kernel_pte_work.list is global shared var, it would make the producer >> pte_free_kernel() and the consumer kernel_pte_work_func() to operate in >> serialized timing. In a large system, I don't think you design this >> deliberately 🙂 >> > Sorry for jumping. > > Agree, unless it is never considered as a hot path or something that can > be really contented. It looks like you can use just a per-cpu llist to drain > thinks. Remember, the code that has to run just before all this sent an IPI to every single CPU on the system to have them do a (on x86 at least) pretty expensive TLB flush. If this is a hot path, we have bigger problems on our hands: the full TLB flush on every CPU. So, sure, there are a million ways to make this deferred freeing more scalable. But the code that's here is dirt simple and self contained. If someone has some ideas for something that's simpler and more scalable, then I'm totally open to it. But this is _not_ the place to add complexity to get scalability.