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Peter Anvin" , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Peter Zijlstra , Adrian Hunter , Kan Liang , Tony Luck , Zhang Rui , Steven Rostedt , Andrew Cooper , "Kirill A . Shutemov" , Jacob Pan , Andi Kleen , Kai Huang , Sandipan Das , linux-perf-users@vger.kernel.org, linux-edac@vger.kernel.org, kvm@vger.kernel.org, linux-pm@vger.kernel.org, linux-trace-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Thu, Jun 12, 2025, Sohil Mehta wrote: > With the IPI handling APIs ready to support the new NMI encoding, encode > the NMI delivery mode directly with the NMI-source vectors to trigger > NMIs. > > Move most of the existing NMI-based IPIs to use the new NMI-source > vectors, except for the microcode rendezvous NMI and the crash reboot > NMI. NMI handling for them is special-cased in exc_nmi() and does not > need NMI-source reporting. > > However, in the future, it might be useful to assign a source vector to > all NMI sources to improve isolation and debuggability. > > Originally-by: Jacob Pan > Suggested-by: Sean Christopherson > Co-developed-by: Xin Li (Intel) > Signed-off-by: Xin Li (Intel) > Signed-off-by: Sohil Mehta > --- > v7: No change. > > v6: Include asm/nmi.h to avoid compile errors. (LKP) > > v5: Encode APIC_DM_NMI directly with the NMI-source vector. > --- > arch/x86/include/asm/apic.h | 8 ++++++++ > arch/x86/kernel/apic/hw_nmi.c | 2 +- > arch/x86/kernel/cpu/mce/inject.c | 2 +- > arch/x86/kernel/kgdb.c | 2 +- > arch/x86/kernel/nmi_selftest.c | 2 +- > arch/x86/kernel/smp.c | 2 +- > 6 files changed, 13 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h > index 32cdd81e5e45..5789df1708bd 100644 > --- a/arch/x86/include/asm/apic.h > +++ b/arch/x86/include/asm/apic.h > @@ -14,6 +14,7 @@ > #include > #include > #include > +#include > #include > > #define ARCH_APICTIMER_STOPS_ON_C3 1 > @@ -23,6 +24,13 @@ > #define APIC_EXTNMI_ALL 1 > #define APIC_EXTNMI_NONE 2 > > +/* Trigger NMIs with source information */ > +#define TEST_NMI (APIC_DM_NMI | NMIS_VECTOR_TEST) > +#define SMP_STOP_NMI (APIC_DM_NMI | NMIS_VECTOR_SMP_STOP) > +#define BT_NMI (APIC_DM_NMI | NMIS_VECTOR_BT) s/BT/BACKTRACE? > +#define KGDB_NMI (APIC_DM_NMI | NMIS_VECTOR_KGDB) > +#define MCE_NMI (APIC_DM_NMI | NMIS_VECTOR_MCE) IMO, NMI_xxx reads better, e.g. it's easier to see that code is sending an NMI at the call sites. > + > /* > * Debugging macros > */ > diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c > index 4e04f13d2de9..586f4b25feae 100644 > --- a/arch/x86/kernel/apic/hw_nmi.c > +++ b/arch/x86/kernel/apic/hw_nmi.c > @@ -33,7 +33,7 @@ u64 hw_nmi_get_sample_period(int watchdog_thresh) > #ifdef arch_trigger_cpumask_backtrace > static void nmi_raise_cpu_backtrace(cpumask_t *mask) > { > - __apic_send_IPI_mask(mask, NMI_VECTOR); > + __apic_send_IPI_mask(mask, BT_NMI); This patch is buggy. There are at least two implementations of ->send_IPI_mask() that this breaks: uv_send_IPI_mask() = > uv_send_IPI_one(): if (vector == NMI_VECTOR) dmode = APIC_DELIVERY_MODE_NMI; else dmode = APIC_DELIVERY_MODE_FIXED; and xen_send_IPI_mask() => xen_map_vector(): switch (vector) { case RESCHEDULE_VECTOR: xen_vector = XEN_RESCHEDULE_VECTOR; break; case CALL_FUNCTION_VECTOR: xen_vector = XEN_CALL_FUNCTION_VECTOR; break; case CALL_FUNCTION_SINGLE_VECTOR: xen_vector = XEN_CALL_FUNCTION_SINGLE_VECTOR; break; case IRQ_WORK_VECTOR: xen_vector = XEN_IRQ_WORK_VECTOR; break; #ifdef CONFIG_X86_64 case NMI_VECTOR: case APIC_DM_NMI: /* Some use that instead of NMI_VECTOR */ xen_vector = XEN_NMI_VECTOR; break; #endif default: xen_vector = -1; printk(KERN_ERR "xen: vector 0x%x is not implemented\n", vector); } return xen_vector; Looking at all of this again, shoving the NMI source information into the @vector is quite brittle. Nothing forces implementations to handle embedded delivery mode information. One thought would be to pass a small struct (by value), and then provide macros to generate the structure for a specific vector. That provides some amount of type safety and should make it a bit harder to pass in garbage, without making the callers any less readable. struct apic_ipi { u8 vector; u8 type; }; #define APIC_IPI(v, t) ({ struct apic_ipi i = { .vector = v, .type = t }; i; }) #define APIC_IPI_IRQ(vector) APIC_IPI(vector, APIC_DELIVERY_MODE_FIXED) #define APIC_IPI_NMI(vector) APIC_IPI(vector, APIC_DELIVERY_MODE_NMI) #define IPI_IRQ_WORK APIC_IPI_IRQ(IRQ_WORK_VECTOR) #define IPI_POSTED_INTR_WAKEUP APIC_IPI_IRQ(POSTED_INTR_WAKEUP_VECTOR) #define IPI_NMI_BACKTRACE APIC_IPI_NMI(NMI_BACKTRACE_VECTOR) static __always_inline void __apic_send_IPI_self(struct apic_ipi ipi)