Changes since v6 ================ This series is a minor update from v6, with the following changes:
* Includes a pre-patch to provide separate KVM IRQ and NMI entry wrappers for FRED (Sean). * Uses an enum to allocate NMI-source vectors (DaveH). * Picks up review tags from Xin. * Rebased on top of 6.16-rc1. The patchset seems to be maturing, so while reviewing this version, please consider providing Acks and Review tags if the patches look okay. v6: https://lore.kernel.org/lkml/20250513203803.2636561-1-sohil.me...@intel.com/ Background ========== NMI-source reporting with FRED [1] provides a new mechanism for identifying the source of NMIs. As part of the FRED event delivery framework, a 16-bit vector bitmap is provided that identifies one or more sources that caused the NMI. Using the source bitmap, the kernel can precisely run the relevant NMI handlers instead of polling the entire NMI handler list. Additionally, the source information would be invaluable for debugging misbehaving handlers and unknown NMIs. Overview of NMI-source usage ============================ Code snippets: // Allocate a static source vector at compile time #define NMIS_VECTOR_TEST 1 // Register an NMI handler with the vector register_nmi_handler(NMI_LOCAL, test_handler, 0, "nmi_test", NMIS_VECTOR_TEST); // Generate an NMI with the source vector using NMI encoded delivery __apic_send_IPI_mask(cpumask, APIC_DM_NMI | NMIS_VECTOR_TEST); // Handle an NMI with or without the source information (oversimplified) source_bitmap = fred_event_data(regs); if (!source_bitmap || (source_bitmap & BIT(NMIS_VECTOR_TEST))) test_handler(); // Unregister handler along with the vector unregister_nmi_handler(NMI_LOCAL, "nmi_test"); Patch structure =============== Patch 1-3: Prepare FRED/KVM and enumerate NMI-source reporting Patch 4-6: Register and handle NMI-source vectors Patch 7-9: APIC changes to generate NMIs with vectors Patch 10: Improve debug print with NMI-source information Many thanks to Sean Christopherson, Xin Li, H. Peter Anvin, Andi Kleen, Tony Luck, Kan Liang, Jacob Pan Jun, Zeng Guang, Peter Zijlstra, Sandipan Das, Steven Rostedt, Dave Hansen and others for their contributions, reviews and feedback. Future work =========== I am considering a few additional changes related to debugging and tracing, as well as KVM support, that would be valuable for enhancing NMI handling in the kernel. Refer the v6 cover letter for more details: v6: https://lore.kernel.org/lkml/20250513203803.2636561-1-sohil.me...@intel.com/ Links ===== [1]: Chapter 9, https://www.intel.com/content/www/us/en/content-details/819481/flexible-return-and-event-delivery-fred-specification.html Jacob Pan (1): perf/x86: Enable NMI-source reporting for perfmon Sean Christopherson (1): x86/fred: Provide separate IRQ vs. NMI wrappers for entry from KVM Sohil Mehta (8): x86/fred: Pass event data to the NMI entry point from KVM x86/cpufeatures: Add the CPUID feature bit for NMI-source reporting x86/nmi: Extend the registration interface to include the NMI-source vector x86/nmi: Assign and register NMI-source vectors x86/nmi: Add support to handle NMIs with source information x86/nmi: Prepare for the new NMI-source vector encoding x86/nmi: Enable NMI-source for IPIs delivered as NMIs x86/nmi: Print source information with the unknown NMI console message arch/x86/entry/entry_64_fred.S | 2 +- arch/x86/events/amd/ibs.c | 2 +- arch/x86/events/core.c | 6 +-- arch/x86/events/intel/core.c | 6 +-- arch/x86/include/asm/apic.h | 39 ++++++++++++++++++ arch/x86/include/asm/apicdef.h | 2 +- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/fred.h | 35 +++++++++++----- arch/x86/include/asm/nmi.h | 62 ++++++++++++++++++++++++++++- arch/x86/kernel/apic/hw_nmi.c | 5 +-- arch/x86/kernel/apic/ipi.c | 4 +- arch/x86/kernel/apic/local.h | 24 ++++++----- arch/x86/kernel/cpu/cpuid-deps.c | 1 + arch/x86/kernel/cpu/mce/inject.c | 4 +- arch/x86/kernel/cpu/mshyperv.c | 2 +- arch/x86/kernel/kgdb.c | 8 ++-- arch/x86/kernel/kvm.c | 9 +---- arch/x86/kernel/nmi.c | 40 +++++++++++++++++++ arch/x86/kernel/nmi_selftest.c | 8 ++-- arch/x86/kernel/smp.c | 6 +-- arch/x86/kvm/vmx/vmx.c | 4 +- arch/x86/platform/uv/uv_nmi.c | 4 +- drivers/acpi/apei/ghes.c | 2 +- drivers/char/ipmi/ipmi_watchdog.c | 3 +- drivers/edac/igen6_edac.c | 3 +- drivers/thermal/intel/therm_throt.c | 2 +- drivers/watchdog/hpwdt.c | 6 +-- 27 files changed, 218 insertions(+), 72 deletions(-) base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494 -- 2.43.0
