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Date: Thu, 22 Jan 2026 12:29:08 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: "xen-devel@lists.xenproject.org" , Andrew Cooper Subject: Re: [PATCH v4 8/8] x86/HPET: don't arbitrarily cap delta in reprogram_hpet_evt_channel() Message-ID: References: <57f34114-54b7-483d-8ac0-e9fa49df959f@suse.com> <37cdba83-9bf8-493a-9a7b-5ec11c32159a@suse.com> <72bff85d-9771-4998-bc80-1efe2d453e6e@suse.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <72bff85d-9771-4998-bc80-1efe2d453e6e@suse.com> X-ClientProxiedBy: MR1P264CA0118.FRAP264.PROD.OUTLOOK.COM (2603:10a6:501:50::25) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|DSWPR03MB989131:EE_ X-MS-Office365-Filtering-Correlation-Id: ce2c2afe-6e7a-4daa-f1bf-08de59a9777b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014; 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> >> > >> - delta = min_t(int64_t, delta, MAX_DELTA_NS); > >> delta = max_t(int64_t, delta, MIN_DELTA_NS); > >> delta = ns2ticks(delta, ch->shift, ch->mult); > >> > >> + if ( delta > UINT32_MAX ) > >> + { > >> + hpet_write32(hpet_read32(HPET_COUNTER), HPET_Tn_CMP(ch->idx)); > > > > Should Xen disable interrupts around this call to avoid unexpected > > latency between the counter read and the comparator write? > > Such latency could then still arise, due NMI or SMI. What's your underlying > concern here? For NMI or SMI there isn't much we can do. I guess this is much less of a concern here than it is in hpet_next_event(), given the next event is expected to be after a full HPET counter period. One of those events taking a full HPET counter period overlap would make a lot of others things explode. Reviewed-by: Roger Pau Monné Thanks, Roger.