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X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?czYLjlllCruUXCjRFl0vYmPUjCJlr7kYMokO8VOzzubM48TK9PeA2fantpBB?= =?us-ascii?Q?bfJgzO4yTDKT3iUIHLdALbX5EO5oWjP1/nzWlk029qnPyD48HE4Z6ZrLBCls?= =?us-ascii?Q?hlUSZKBBMJNHm0h6tZOMudBY2jYOLB/0T1Da/9LRNRzkmuDo2R4mpPscJzxd?= =?us-ascii?Q?753fZol9pYuJvI3+6Q+DTWuP1l8CbkPrW+NQHh0FOMd8WiaOxUYSE5UlP7G1?= =?us-ascii?Q?I8oqNgy6ep19p6d/ySwbQwNV2Ha+N/PM31tLUiuJMkGp0BAVX/9v0ZimI2ZL?= =?us-ascii?Q?RUWP4fIaHt1oSzqNQNT/slNVjFZAcTVkVpDEAydSjXEa7oIl/aSWqfWUzxPP?= =?us-ascii?Q?gLvfFtRdr0uDJyLrvU0iNEf8p3QkjpNZ20jqhfGD7iOQoHbAti87DvGN2VtJ?= =?us-ascii?Q?wJres6zLq3jCOC8u1wCU5ZEX74aE+mdvvjUGjBFETb8e3Pzo6JF0xaI5Oj/R?= =?us-ascii?Q?X6FuLZsWrBdPJx4Ft0R6+dVsVatqovGaZJOUHXGndVtbfgVmgoisx0cicrfZ?= =?us-ascii?Q?ZD9+YJswunoXHdlU32RZ5Re0GsEqYLeu0/pV6rPcDpUnFgamF9QTwqcrG/dj?= =?us-ascii?Q?osacmQYNBBIsnZgaEe96DSQgU/NFwfXUlmX8oKOxf+ND1fmV81v4tm5V8NRq?= =?us-ascii?Q?P5J7zoO56+aXfPAvqOONnuiIGPHM2TK23XGz5leDVB6Ituz0vc9EgyDUdv33?= =?us-ascii?Q?ORV2E4ijClBoSx+pV664hWO0kOoDIuKkdrGBFXfuWNnc2XAiu/qPHSIiMa1b?= =?us-ascii?Q?NjgWc1jAL3YdgbxWavomIkMGKbm0bdaPIwsPxItInpa2geuEUe1REwe9LLfA?= =?us-ascii?Q?VBoWUqQjKf68DIIjzkspuKi5zG2dQIrL6ji5nFTa9PqlUXpA+8qPdnQeooDZ?= =?us-ascii?Q?wppQeCDrai13qjE/QEc5K2m7QYcKZiQHgX4cwvE/ab8vHxGpq+eAU1VnrnkU?= =?us-ascii?Q?4MHGJZFSeLgKNz46AzJEyoNPzt7Wj8fAmuPTd5o5t/clgeJ9fLJCm8x/Ms4G?= =?us-ascii?Q?Z0TlzULuCeej2Lq4AunNrdHgqayokFuL5tyXfTQ+yQRAcpTGIZt6ZQZllWyH?= =?us-ascii?Q?f1nOH/wCNdlfooVBU6XuAxnNCsLnBpmLKfA561f2iAvnoICFb5auSO5xjfsy?= =?us-ascii?Q?eI4CHKXzXjKTxZcp5LZYPusUZeqVlGn+F4yR08cH0Z4R4FFbZGfEhNSPm8Fs?= =?us-ascii?Q?Q5s/2GJ9hvOvJSloze83ROIf69W9/LVsaMWobt3R0oNpAxGtsDzdKf1GW5ha?= =?us-ascii?Q?7qqw3LogwI5jhITS1xZv3stwIjQeWjS1AoaLSllcdmui/qBcsh6ML3yXM/yR?= =?us-ascii?Q?1qA3wxriZPElZJVgYUtDIY2nK6FR10gIUKhi94cMywDgsYmhJwK3QsNn43XG?= =?us-ascii?Q?JwxBUZU93UqAP5ys9O2ZGVL+zm37WNcFk2Buud44Z6/fs3CH1UpVHLv3ZYjC?= =?us-ascii?Q?ugkXwR/XeJx0ULMw0ZVyEOE6EDkIOgyj9D6D5Bcos1c21q3z2acqmEv/N278?= =?us-ascii?Q?gWxSNWA/vQMghD/fUInIDU2yjwyXrd1rt9OC?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(376014)(82310400026)(36860700013)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jul 2025 00:07:31.9609 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 587f837e-7313-475c-5a4d-08ddbdb36f44 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B374.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR12MB9265 X-ZohoMail-DKIM: pass (identity @amd.com) X-ZM-MESSAGEID: 1751933268983116600 Content-Type: text/plain; charset="utf-8" On real time configuration with the null scheduler, we shouldn't interrupt the guest execution unless strictly necessary: the guest could be a real time guest (e.g. FreeRTOS) and interrupting its execution could lead to a missed deadline. The principal source of interruptions is IPIs. Remove the unnecessary IPI on all physical CPUs to sync the TSC when the TSC is known to be reliable. Signed-off-by: Stefano Stabellini --- xen/arch/x86/time.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index 59129f419d..bfd022174a 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -2303,6 +2303,10 @@ static void cf_check time_calibration(void *unused) local_irq_enable(); } =20 + if ( boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && + boot_cpu_has(X86_FEATURE_TSC_RELIABLE) ) + return; + cpumask_copy(&r.cpu_calibration_map, &cpu_online_map); =20 /* @wait=3D1 because we must wait for all cpus before freeing @r. */ --=20 2.25.1 From nobody Thu Oct 30 23:28:27 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; arc=pass (i=1 dmarc=pass fromdomain=amd.com); dmarc=pass(p=quarantine dis=none) header.from=amd.com ARC-Seal: i=2; a=rsa-sha256; t=1751933272; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jul 2025 00:07:32.8728 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 27fc646e-75e7-4932-8f18-08ddbdb36fcf X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B36E.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PPFAF4999BF6 X-ZohoMail-DKIM: pass (identity @amd.com) X-ZM-MESSAGEID: 1751933274782116600 Content-Type: text/plain; charset="utf-8" Today, checking for non-fatal MCE errors on ARM is very invasive: it involves a periodic timer interrupting the physical CPU execution at regular intervals. Moreover, when the timer fires, the handler sends an IPI to all physical CPUs. Both these actions are disruptive in terms of latency and deterministic execution times for real-time workloads. They might miss a deadline due to one of these IPIs. Make it possible to disable non-fatal MCE errors checking with a new Kconfig option (AMD_MCE_NONFATAL). Signed-off-by: Stefano Stabellini --- RFC. I couldn't find a better way to do this. --- xen/arch/x86/Kconfig.cpu | 15 +++++++++++++++ xen/arch/x86/cpu/mcheck/amd_nonfatal.c | 3 ++- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/Kconfig.cpu b/xen/arch/x86/Kconfig.cpu index 5fb18db1aa..14e20ad19d 100644 --- a/xen/arch/x86/Kconfig.cpu +++ b/xen/arch/x86/Kconfig.cpu @@ -10,6 +10,21 @@ config AMD May be turned off in builds targetting other vendors. Otherwise, must be enabled for Xen to work suitably on AMD platforms. =20 +config AMD_MCE_NONFATAL + bool "Check for non-fatal MCEs on AMD CPUs" + default y + depends on AMD + help + Check for non-fatal MCE errors. + + When this option is on (default), Xen regularly checks for + non-fatal MCEs potentially occurring on all physical CPUs. The + checking is done via timers and IPI interrupts, which is + acceptable in most configurations, but not for real-time. + + Turn this option off if you plan on deploying real-time workloads + on Xen. + config INTEL bool "Support Intel CPUs" default y diff --git a/xen/arch/x86/cpu/mcheck/amd_nonfatal.c b/xen/arch/x86/cpu/mche= ck/amd_nonfatal.c index 7d48c9ab5f..812e18f612 100644 --- a/xen/arch/x86/cpu/mcheck/amd_nonfatal.c +++ b/xen/arch/x86/cpu/mcheck/amd_nonfatal.c @@ -191,7 +191,8 @@ static void cf_check mce_amd_work_fn(void *data) =20 void __init amd_nonfatal_mcheck_init(struct cpuinfo_x86 *c) { - if (!(c->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON))) + if ( !IS_ENABLED(CONFIG_AMD_MCE_NONFATAL) || + (!(c->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON))) ) return; =20 /* Assume we are on K8 or newer AMD or Hygon CPU here */ --=20 2.25.1