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X-IronPort-AV: E=McAfee;i="6600,9927,10734"; a="355886183" X-IronPort-AV: E=Sophos;i="6.00,224,1681196400"; d="scan'208";a="355886183" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jun 2023 09:05:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10734"; a="799436682" X-IronPort-AV: E=Sophos;i="6.00,224,1681196400"; d="scan'208";a="799436682" Received: from vsmyers-mobl2.amr.corp.intel.com (HELO [10.212.146.233]) ([10.212.146.233]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jun 2023 09:05:15 -0700 Message-ID: <0600959d-9e10-fb1f-b3a9-862a51b9d8e1@intel.com> Date: Wed, 7 Jun 2023 09:05:14 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v11 11/20] x86/virt/tdx: Fill out TDMRs to cover all TDX memory regions Content-Language: en-US To: Kai Huang , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: linux-mm@kvack.org, kirill.shutemov@linux.intel.com, tony.luck@intel.com, peterz@infradead.org, tglx@linutronix.de, seanjc@google.com, pbonzini@redhat.com, david@redhat.com, dan.j.williams@intel.com, rafael.j.wysocki@intel.com, ying.huang@intel.com, reinette.chatre@intel.com, len.brown@intel.com, ak@linux.intel.com, isaku.yamahata@intel.com, chao.gao@intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, bagasdotme@gmail.com, sagis@google.com, imammedo@redhat.com References: <927ec9871721d2a50f1aba7d1cf7c3be50e4f49b.1685887183.git.kai.huang@intel.com> From: Dave Hansen In-Reply-To: <927ec9871721d2a50f1aba7d1cf7c3be50e4f49b.1685887183.git.kai.huang@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: AC33B40022 X-Stat-Signature: by6zp4x7rh5nmnyh1a4a5kp6h1bw5at7 X-HE-Tag: 1686154115-723086 X-HE-Meta: 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 h4D/sYhC fyyoc5JNAjUWg8PwbB5qABWzEc4qlsAJkB+Y0RKZ2eVaP7YHRqG2P3wNbJ2O+I32g3OErQleNTOTuqG6uiB0BVvtWjKEexC+sHSUAvfG4KdQyAoc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000367, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 6/4/23 07:27, Kai Huang wrote: > + /* > + * Loop over TDX memory regions and fill out TDMRs to cover them. > + * To keep it simple, always try to use one TDMR to cover one > + * memory region. > + * > + * In practice TDX1.0 supports 64 TDMRs, which is big enough to > + * cover all memory regions in reality if the admin doesn't use > + * 'memmap' to create a bunch of discrete memory regions. When > + * there's a real problem, enhancement can be done to merge TDMRs > + * to reduce the final number of TDMRs. > + */ Rather than focus in on one specific command-line parameter, let's just say: In practice TDX supports at least 64 TDMRs. A 2-socket system typically only consumes of those. This code is dumb and simple and may use more TMDRs than is strictly required. Let's also put a pr_warn() in here if we exceed, say 1/2 or maybe 3/4 of the 64. We'll hopefully start to get reports somewhat in advance if systems get close to the limit.