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X-CSE-ConnectionGUID: NN6AtLwGTn6YLCqfTfqOMQ== X-CSE-MsgGUID: o4fT4Fj4SBiqyiFliIeWwA== X-IronPort-AV: E=McAfee;i="6700,10204,11322"; a="48411916" X-IronPort-AV: E=Sophos;i="6.13,222,1732608000"; d="scan'208";a="48411916" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Jan 2025 10:48:43 -0800 X-CSE-ConnectionGUID: FrATxFAvTc2EnTZZKk2kZg== X-CSE-MsgGUID: tB/ivjkCTEui2qoF6uxsxA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="107793719" Received: from gargmani-mobl1.amr.corp.intel.com (HELO [10.124.222.89]) ([10.124.222.89]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Jan 2025 10:48:42 -0800 Message-ID: <672ff78c-d93f-48d9-936e-e86b3d9d9dbc@intel.com> Date: Tue, 21 Jan 2025 10:48:44 -0800 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 v6 09/12] x86/mm: enable broadcast TLB invalidation for multi-threaded processes To: Peter Zijlstra , Rik van Riel Cc: x86@kernel.org, linux-kernel@vger.kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, zhengqi.arch@bytedance.com, nadav.amit@gmail.com, thomas.lendacky@amd.com, kernel-team@meta.com, linux-mm@kvack.org, akpm@linux-foundation.org, jannh@google.com, mhklinux@outlook.com, andrew.cooper3@citrix.com References: <20250120024104.1924753-1-riel@surriel.com> <20250120024104.1924753-10-riel@surriel.com> <20250121095507.GB5388@noisy.programming.kicks-ass.net> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/21/25 01:55, Peter Zijlstra wrote: > Can't we just start with a very simple constant test and poke at things > if/when its found to not work? I'd prefer something simpler for now, too. Let's just pick a sane number, maybe 16 or 32 for now, make it pokeable in debugfs and make sure we have a way to tell when the PCID space is exhausted. Then we try and design a solution for the _actual_ cases where folks are exhausting it.