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Peter Anvin" , Suresh Siddha , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Broadcom internal kernel review list , Paolo Bonzini , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky References: <20260202-x2apic-fix-v1-0-71c8f488a88b@sony.com> <20260202-x2apic-fix-v1-2-71c8f488a88b@sony.com> Content-Language: en-GB From: Andrew Cooper In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: LO4P265CA0292.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:38f::18) To CH8PR03MB8275.namprd03.prod.outlook.com (2603:10b6:610:2b9::7) Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH8PR03MB8275:EE_|DS2PR03MB8418:EE_ X-MS-Office365-Filtering-Correlation-Id: 03d7229a-38da-4c35-8ac0-08de62545c54 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|10070799003|1800799024|921020; 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This statement is misleading and has been argued over before.  It's missing the key word "all". What IR gets you in this case is the ability to target CPU 255 and higher. The OS-side access mechanism (xAPIC MMIO vs x2APIC MSRs) has no baring on how external interrupts are handled in the fabric. There are plenty of good reasons to have Interrupt Remapping enabled when available, but it is not a hard requirement architecturally. ~Andrew