From a3a607f33f81c3ce3e3e0eaa2fe97d263278b464 Mon Sep 17 00:00:00 2001 From: Roger Pau Monne Date: Mon, 14 Apr 2025 15:57:55 +0200 Subject: [PATCH] x86/boot: attempt to print trace and panic on AP bring up stall MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit With the current AP bring up code, Xen can get stuck indefinitely if an AP freezes during boot after the 'callin' step. Introduce a 5s timeout while waiting for APs to finish startup. On failure of an AP to complete startup, send an NMI to trigger the printing of a stack backtrace on the stuck AP and panic on the BSP. This patch was done while investigating the issue caused by Intel erratum ICX143. It wasn't helpful in that case, but it's still and improvement when debugging AP bring up related issues. Signed-off-by: Roger Pau Monné Reviewed-by: Andrew Cooper --- xen/arch/x86/smpboot.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c index adcaec6899..a90caf45a5 100644 --- a/xen/arch/x86/smpboot.c +++ b/xen/arch/x86/smpboot.c @@ -1375,6 +1375,7 @@ int cpu_add(uint32_t apic_id, uint32_t acpi_id, uint32_t pxm) int __cpu_up(unsigned int cpu) { int apicid, ret; + s_time_t start; if ( (apicid = x86_cpu_to_apicid[cpu]) == BAD_APICID ) return -ENODEV; @@ -1393,10 +1394,18 @@ int __cpu_up(unsigned int cpu) time_latch_stamps(); set_cpu_state(CPU_STATE_ONLINE); + start = NOW(); while ( !cpu_online(cpu) ) { cpu_relax(); process_pending_softirqs(); + if ( (NOW() - start) > SECONDS(5) ) + { + /* AP is stuck, send NMI and panic. */ + show_execution_state_nmi(cpumask_of(cpu), true); + panic("APIC ID %#x (CPU%u) stuck while starting up\n", + apicid, cpu); + } } return 0;