From 9cab5fb776d4367e26950cf759211e948335288e Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 2 Oct 2023 14:00:07 +0200 Subject: [PATCH] x86/apic: Provide apic_force_nmi_on_cpu() When SMT siblings are soft-offlined and parked in one of the play_dead() variants they still react on NMI, which is problematic on affected Intel CPUs. The default play_dead() variant uses MWAIT on modern CPUs, which is not guaranteed to be safe when updated concurrently. Right now late loading is prevented when not all SMT siblings are online, but as they still react on NMI, it is possible to bring them out of their park position into a trivial rendezvous handler. Provide a function which allows to do that. I does sanity checks whether the target is in the cpus_booted_once_mask and whether the APIC driver supports it. Mark X2APIC and XAPIC as capable, but exclude 32bit and the UV and NUMACHIP variants as that needs feedback from the relevant experts. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20231002115903.603100036@linutronix.de --- arch/x86/include/asm/apic.h | 5 ++++- arch/x86/kernel/apic/apic_flat_64.c | 2 ++ arch/x86/kernel/apic/ipi.c | 8 ++++++++ arch/x86/kernel/apic/x2apic_cluster.c | 1 + arch/x86/kernel/apic/x2apic_phys.c | 1 + 5 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 5af4ec1a0f71c..17f2f28a495ec 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -276,7 +276,8 @@ struct apic { u32 disable_esr : 1, dest_mode_logical : 1, - x2apic_set_max_apicid : 1; + x2apic_set_max_apicid : 1, + nmi_to_offline_cpu : 1; u32 (*calc_dest_apicid)(unsigned int cpu); @@ -542,6 +543,8 @@ extern bool default_check_apicid_used(physid_mask_t *map, int apicid); extern void default_ioapic_phys_id_map(physid_mask_t *phys_map, physid_mask_t *retmap); extern int default_cpu_present_to_apicid(int mps_cpu); +void apic_send_nmi_to_offline_cpu(unsigned int cpu); + #else /* CONFIG_X86_LOCAL_APIC */ static inline unsigned int read_apic_id(void) { return 0; } diff --git a/arch/x86/kernel/apic/apic_flat_64.c b/arch/x86/kernel/apic/apic_flat_64.c index 032a84e2c3ccc..cd16228611ce8 100644 --- a/arch/x86/kernel/apic/apic_flat_64.c +++ b/arch/x86/kernel/apic/apic_flat_64.c @@ -103,6 +103,7 @@ static struct apic apic_flat __ro_after_init = { .send_IPI_allbutself = default_send_IPI_allbutself, .send_IPI_all = default_send_IPI_all, .send_IPI_self = default_send_IPI_self, + .nmi_to_offline_cpu = true, .read = native_apic_mem_read, .write = native_apic_mem_write, @@ -175,6 +176,7 @@ static struct apic apic_physflat __ro_after_init = { .send_IPI_allbutself = default_send_IPI_allbutself, .send_IPI_all = default_send_IPI_all, .send_IPI_self = default_send_IPI_self, + .nmi_to_offline_cpu = true, .read = native_apic_mem_read, .write = native_apic_mem_write, diff --git a/arch/x86/kernel/apic/ipi.c b/arch/x86/kernel/apic/ipi.c index a44ba7209ef3a..edad86f32e38c 100644 --- a/arch/x86/kernel/apic/ipi.c +++ b/arch/x86/kernel/apic/ipi.c @@ -97,6 +97,14 @@ sendmask: __apic_send_IPI_mask(mask, CALL_FUNCTION_VECTOR); } +void apic_send_nmi_to_offline_cpu(unsigned int cpu) +{ + if (WARN_ON_ONCE(!apic->nmi_to_offline_cpu)) + return; + if (WARN_ON_ONCE(!cpumask_test_cpu(cpu, &cpus_booted_once_mask))) + return; + apic->send_IPI(cpu, NMI_VECTOR); +} #endif /* CONFIG_SMP */ static inline int __prepare_ICR2(unsigned int mask) diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c index affbff65e4971..a8306089c91bc 100644 --- a/arch/x86/kernel/apic/x2apic_cluster.c +++ b/arch/x86/kernel/apic/x2apic_cluster.c @@ -251,6 +251,7 @@ static struct apic apic_x2apic_cluster __ro_after_init = { .send_IPI_allbutself = x2apic_send_IPI_allbutself, .send_IPI_all = x2apic_send_IPI_all, .send_IPI_self = x2apic_send_IPI_self, + .nmi_to_offline_cpu = true, .read = native_apic_msr_read, .write = native_apic_msr_write, diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c index 788cdb4ee394d..c8ac1b12b8ac6 100644 --- a/arch/x86/kernel/apic/x2apic_phys.c +++ b/arch/x86/kernel/apic/x2apic_phys.c @@ -166,6 +166,7 @@ static struct apic apic_x2apic_phys __ro_after_init = { .send_IPI_allbutself = x2apic_send_IPI_allbutself, .send_IPI_all = x2apic_send_IPI_all, .send_IPI_self = x2apic_send_IPI_self, + .nmi_to_offline_cpu = true, .read = native_apic_msr_read, .write = native_apic_msr_write, -- 2.30.2