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X-CSE-ConnectionGUID: q2F8qd4sT0OQ5o9GfqEiqQ== X-CSE-MsgGUID: HHq2P1fnRxGzvRxjd9ZEdw== X-IronPort-AV: E=McAfee;i="6700,10204,11322"; a="38070861" X-IronPort-AV: E=Sophos;i="6.13,222,1732608000"; d="scan'208";a="38070861" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Jan 2025 09:14:33 -0800 X-CSE-ConnectionGUID: Lbc8nTfpQB6esZn9hjwNXQ== X-CSE-MsgGUID: IMmYhpiMRdi7jGiC6o6E5A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,222,1732608000"; d="scan'208";a="106978906" Received: from gargmani-mobl1.amr.corp.intel.com (HELO [10.124.222.89]) ([10.124.222.89]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Jan 2025 09:14:32 -0800 Message-ID: <01cba8ef-b68f-4074-9a7b-7258eaee3893@intel.com> Date: Tue, 21 Jan 2025 09:14:32 -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 v5 00/12] AMD broadcast TLB invalidation To: Michael Kelley , "riel@surriel.com" , "x86@kernel.org" Cc: "linux-kernel@vger.kernel.org" , "bp@alien8.de" , "peterz@infradead.org" , "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" , "andrew.cooper3@citrix.com" References: <20250116023127.1531583-1-riel@surriel.com> 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 1/16/25 10:14, Michael Kelley wrote: > So CoCo VMs may still use the paravirtualization that makes > hypercalls to do TLB flushes. It's future work to *always* use > INVLPGB (if available) in a CoCo VM. How would this actually work, though? One of the reasons that we have the whole TLB_NR_DYN_ASIDS mechanism is that picking a PCID to shove in CR3 is an entirely CPU local operation. The PCID is in a CPU-local namespace and nobody else cares what it is. Rik obviously now has a system-wide set of IDs which are globally visible and globally valid. But his mechanism is also a bit choosy so that the global resource management doesn't get to be a choke point. But if we move to INVLPGB-only, we're all of a sudden *forced* to do some kind of wide global resource management, even for single-threaded processes. Rik doesn't have a scheme for that in the current set. So I think this would be a whole separate conversation from this series.