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Mon, 12 Jun 2023 14:18:01 +0100 From: David Laight To: "'kirill.shutemov@linux.intel.com'" , "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 Thread-Topic: [PATCH v11 18/20] x86: Handle TDX erratum to reset TDX private memory during kexec() and reboot Thread-Index: AQHZnSRWXDaSmJ22okO690LL2Ubsg6+HJc9w Date: Mon, 12 Jun 2023 13:18:01 +0000 Message-ID: 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> <20230612114843.n7vvoh7m2rk4la56@box.shutemov.name> In-Reply-To: <20230612114843.n7vvoh7m2rk4la56@box.shutemov.name> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 9067F160016 X-Rspam-User: X-Stat-Signature: 6ioo3gm3oqi9fcoq3jzybw9jwh3ebrbd X-Rspamd-Server: rspam03 X-HE-Tag: 1686575899-765872 X-HE-Meta: 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 1MTIEXzO tkPAzyfLR3++fvNuWAoDUMM/rjW5GYqt1qmTvYWjdOEKx84og7bGDLEmxw87Ezlbehyn4iVzBuAStJttE91Kdias2wvrnlZWSZfxLWkQDfyJhm9fpsLtctqtY/v2EV3vSjHo+ayU7IsoAa+k/wlywMpoI8Sh6aLRfedwBxiym6LIuVgSKZvq9ZfkpgVU/xdrEAAykSZGBn027UjveR3N4ruLdtsDrQsGYSJzdLyaKK+27wOe0sy5KHes3QwIBtpCeuEna 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: From: kirill.shutemov@linux.intel.com > Sent: 12 June 2023 12:49 >=20 > On Mon, Jun 12, 2023 at 10:27:44AM +0000, Huang, Kai wrote: > > Does it make sense? >=20 > I understand your logic. AFAICS, it is correct (smp_mb() instead of __mb(= ) > would be better), but it is not justified from complexity PoV. Given that x86 performs writes pretty much in code order. Do you need anything more than a compile barrier? > This lockless exercise gave me a pause to understand. >=20 > Lockless doesn't buy you anything here, only increases complexity. > Just take a lock. Indeed... =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)