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Date: Thu, 22 Jan 2026 11:23:43 +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> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <37cdba83-9bf8-493a-9a7b-5ec11c32159a@suse.com> X-ClientProxiedBy: PR3P193CA0050.EURP193.PROD.OUTLOOK.COM (2603:10a6:102:51::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_|DM6PR03MB5177:EE_ X-MS-Office365-Filtering-Correlation-Id: 205086a2-d452-405e-13a1-08de59a05443 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7053199007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?eTJNY1JSM2JjTk9rMWNtMU9xVDdrQlZtNFVIR3c4NUdlM014OGVXTktuVzRB?= =?utf-8?B?WHZFVVMxeG9mVlN2RlRmUWFxSHdTcGcrVFM2U0VZeEZ3S3FuTm1PaTVocFd0?= =?utf-8?B?OGRQdDBZNk80SWp2Tlk0djE4amw4U2FHTXpvZXQ4MDRDMEx3UU80RnkrZFlG?= =?utf-8?B?VnQvSi8zcm11cnZQK2JQUys0UUVLeTdLY3JSRlR4TDB4STJxbTRoZEpCQ0ZE?= =?utf-8?B?ajN1YVE5SXNLUVRSbFFhbFJ6d253RGk3THdxcEpDRmc4UzB2Mm9pcEJCNGgr?= =?utf-8?B?TG5EdTZTZVpveG0xQksvZWlZK3JkSlRWbHdmRHlEcWRWazY1K080Z2RkYXZ6?= =?utf-8?B?UnBuUnNnalVGRmxrMFFRSmJFSHZDZy9HWEhhcDhhd2xielIwbGxxSnYxL3k4?= =?utf-8?B?ZjNjd0JUdGxvelhWbjJKZG9SWEo5cjV0bFhxSWtHVmNPbDNCcWtDbnNRWjVn?= =?utf-8?B?aWNIQVBLWFdPeG9PU3prSHc1R0JTV1lSSFNEUGUxR01WRnlXaEdYcEJkMTM2?= =?utf-8?B?M1llQUcxTjRPMXUyWjJSMXp3QTR2OG1mM055aFJJN0gvOUFySWxlMldjU0VB?= =?utf-8?B?b1pGK09tUGN0bFIxa3lleGR5WU5KTU44NVdrSjc2b09kZlZBdy9rZWRFV29W?= =?utf-8?B?dkxicmZZUDFmekw1Z1FKR1pNRlBuUFUvSU9OSGw1cnNtU1JjM0w2alFrVHFm?= =?utf-8?B?dE90K2Z5bUwxdDVScVF3NG95N0h5TEZsWVU0dFN4UEpZcXJIRnJ5YVlHQ1U1?= =?utf-8?B?OHNERXJHQzZnQVI2RDkwSEZVbFh3aUVpTTFhR3I5WDR3NTljcnFPcGFmbUpE?= =?utf-8?B?RUtVYmUyanVUWGJBdG5QZjg0RGhPSTZoTmhJWTRCYkducHZwYm80YjZQSVZ5?= =?utf-8?B?RmtSdWNUK0xLc2J2bzRWcm1Ocmt5RFBXVXpMZU9CelhhcUVuNU1RcUF2Qkcy?= =?utf-8?B?TDRjTVBRNmNoQ3A4VDk2OE5RQWdKeHNPSDhGTitoNzJzZ3AxUUZ1aUdERnB5?= =?utf-8?B?MG5lbXdLdGpKWFZjUHdqTDJmdXUzRmlNSU5NZlc3OXpVQ3BiS0t6cGRGcUhw?= =?utf-8?B?ZlZJbDB4VnUxUW1jM3l4aTI5MFhaOTBMZ2lva0Z3S0hmRVozTjNSMlR2MnU0?= =?utf-8?B?bW9DUXdPa3c5MElPWXd5NW0zTzVKc2xaZUZZeUJkUDF4bkExNWNsVFpFQVJV?= =?utf-8?B?aEljUWZYNSt2VXIxd0lES2o2UkVqemwrN0Rub1JpZmc2TDBxck8wQ0dlclVF?= =?utf-8?B?OGNBYmc3bDRmbU1HYjQwMXViVjk4aVB5ckNkL1dXblF5bzhUUG5mZGNtY1VB?= =?utf-8?B?NkNkZ3FBektHb09kR3BwSWxxZFZBb2hoUExzU1hkZHlpRGJkQzI0cFQzY3ZB?= =?utf-8?B?eW10T2pYaDRjaGkzTDBOMVUwbkhrREZ2K3Z0Slk5elFTOEsvUnlBbytIL2VN?= =?utf-8?B?MEhqWkZjZVRUVmFpZkpQdS9pOFRMcDJ2SFFncVAvRU9QeTN2SnM1RXhqWmNM?= =?utf-8?B?eks0bVVweGFHVjlvcWlrTElvOHEwUlFxdXBDMlJDQnUrUU02ZmV4RXlLOXVT?= =?utf-8?B?V0VhM0N3SHltSGh4cm1xdTU2b1ZNK3hMeHFscStBZGhXdTduYmNYc3hrNWYw?= =?utf-8?B?Tms3bkExMmY5RENOQ3JKNDQ4eDVNU3hmUWNkb3M2RW5OSVJReERkSzlZWnNn?= =?utf-8?B?ZnN4d1hvdS94dG5SVklWcGh2REh1TWdWTDVLN1FhOTVRV0pQUFNWZ0FoQTV6?= =?utf-8?B?VlZuNTIvT01OUGkra0pyUU0wYzd3ZUtqSjYrN1RmY1ZwQXNSby96VVgxMFEz?= =?utf-8?B?Q1NrdXdMWFJMeWlxbGlmZzJZd21UVk9ZSWRDL0NZRXpDVzFQSHdPamcrUnQr?= =?utf-8?B?VHZmYzlrTmUveWkvTlc2alN4RGtaNHdOTGVpN0Y1VnhFTVZtMnFHang2d1kv?= =?utf-8?B?akZHUjhHSjdNQk9HSlNJLzFPdklqbE9jRmhjQ2VSSEpPM29ycGU1QXhIWjVR?= =?utf-8?B?cXlvMXVaZEJQMWU4akNsUFRsbS9BRzdZUkhaeHJycys2K0kvdG14Uk0zOFdE?= =?utf-8?B?YThrVVpXRmE5aFYxNWRkVGxvMW9SazBkdjVIanlDMTUxTU94b3hkdTJBTXRI?= =?utf-8?Q?qTT8=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH7PR03MB7860.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(7053199007);DIR:OUT;SFP:1101; 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We can > simply set the comparator such that it'll take a whole cycle through all > 32-bit values until the next interrupt would be raised. (For an extremely > fast-running HPET [400 MHz and up] 10 seconds would also be too long.) > > Signed-off-by: Jan Beulich > --- > v4: New. > > --- a/xen/arch/x86/hpet.c > +++ b/xen/arch/x86/hpet.c > @@ -23,7 +23,6 @@ > #include > #include > > -#define MAX_DELTA_NS MILLISECS(10*1000) > #define MIN_DELTA_NS MICROSECS(20) > > #define HPET_EVT_USED_BIT 0 > @@ -162,10 +161,15 @@ static int reprogram_hpet_evt_channel( > > ch->next_event = expire; > > - 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? Thanks, Roger.