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X-IronPort-AV: E=McAfee;i="6600,9927,10738"; a="360501369" X-IronPort-AV: E=Sophos;i="6.00,236,1681196400"; d="scan'208";a="360501369" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jun 2023 04:48:51 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10738"; a="740998332" X-IronPort-AV: E=Sophos;i="6.00,236,1681196400"; d="scan'208";a="740998332" Received: from smizr3x-mobl3.ger.corp.intel.com (HELO box.shutemov.name) ([10.249.43.127]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jun 2023 04:48:46 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id 4FE6610CC1C; Mon, 12 Jun 2023 14:48:43 +0300 (+03) Date: Mon, 12 Jun 2023 14:48:43 +0300 From: "kirill.shutemov@linux.intel.com" To: "Huang, Kai" Cc: "kvm@vger.kernel.org" , "Hansen, Dave" , "david@redhat.com" , "bagasdotme@gmail.com" , "ak@linux.intel.com" , "Wysocki, Rafael J" , "Luck, Tony" , "Chatre, Reinette" , "Christopherson,, Sean" , "pbonzini@redhat.com" , "tglx@linutronix.de" , "Yamahata, Isaku" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "Shahar, Sagi" , "peterz@infradead.org" , "imammedo@redhat.com" , "Gao, Chao" , "Brown, Len" , "sathyanarayanan.kuppuswamy@linux.intel.com" , "Huang, Ying" , "Williams, Dan J" Subject: Re: [PATCH v11 18/20] x86: Handle TDX erratum to reset TDX private memory during kexec() and reboot Message-ID: <20230612114843.n7vvoh7m2rk4la56@box.shutemov.name> References: <5aa7506d4fedbf625e3fe8ceeb88af3be1ce97ea.1685887183.git.kai.huang@intel.com> <20230609132301.uvvp27yr5kpenl6f@box.shutemov.name> <58f34b4b81b6d6b37d3386dec0f073e6eb7a97ff.camel@intel.com> <20230612075830.jbrdd6ysz4qq7wdf@box.shutemov.name> <4c7effc3abe71aa1cbee41f3bd46b97aed40be26.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4c7effc3abe71aa1cbee41f3bd46b97aed40be26.camel@intel.com> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B8641C0013 X-Stat-Signature: 8dmw5xyrqgerkqw66crachgyk4mx38ft X-HE-Tag: 1686570533-205696 X-HE-Meta: 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 iZNbeHKj IxJy6q8COsBM8DzR1Cv1R7+cGscdy5h6cq4qJOSdRZs6JQQICqWKCEL728h8ej4CewrV/QjXEdHemi422HKh6VftD2lfTBMRL6LJekTQf9DEvesnJIlB6hbiBbTmjVFQyluXuR1ifnTwucaZ/qEqS4S+4AdYV90vGhaWY X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 12, 2023 at 10:27:44AM +0000, Huang, Kai wrote: > Does it make sense? I understand your logic. AFAICS, it is correct (smp_mb() instead of __mb() would be better), but it is not justified from complexity PoV. This lockless exercise gave me a pause to understand. Lockless doesn't buy you anything here, only increases complexity. Just take a lock. Kernel is big. I'm sure you'll find a better opportunity to be clever about serialization :P -- Kiryl Shutsemau / Kirill A. Shutemov