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8d25b7beca
kvm_arch_vcpu_ioctl_run is already doing srcu_read_lock/unlock in two places, namely vcpu_run and post_kvm_run_save, and a third is actually needed around the call to vcpu->arch.complete_userspace_io to avoid the following splat: WARNING: suspicious RCU usage arch/x86/kvm/pmu.c:190 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by CPU 28/KVM/370841: #0: ff11004089f280b8 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x87/0x730 [kvm] Call Trace: <TASK> dump_stack_lvl+0x59/0x73 reprogram_fixed_counter+0x15d/0x1a0 [kvm] kvm_pmu_trigger_event+0x1a3/0x260 [kvm] ? free_moved_vector+0x1b4/0x1e0 complete_fast_pio_in+0x8a/0xd0 [kvm] This splat is not at all unexpected, since complete_userspace_io callbacks can execute similar code to vmexits. For example, SVM with nrips=false will call into the emulator from svm_skip_emulated_instruction(). While it's tempting to never acquire kvm->srcu for an uninitialized vCPU, practically speaking there's no penalty to acquiring kvm->srcu "early" as the KVM_MP_STATE_UNINITIALIZED path is a one-time thing per vCPU. On the other hand, seemingly innocuous helpers like kvm_apic_accept_events() and sync_regs() can theoretically reach code that might access SRCU-protected data structures, e.g. sync_regs() can trigger forced existing of nested mode via kvm_vcpu_ioctl_x86_set_vcpu_events(). Reported-by: Like Xu <likexu@tencent.com> Co-developed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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|---|---|---|
| .. | ||
| mmu | ||
| svm | ||
| vmx | ||
| cpuid.c | ||
| cpuid.h | ||
| debugfs.c | ||
| emulate.c | ||
| fpu.h | ||
| hyperv.c | ||
| hyperv.h | ||
| i8254.c | ||
| i8254.h | ||
| i8259.c | ||
| ioapic.c | ||
| ioapic.h | ||
| irq.c | ||
| irq.h | ||
| irq_comm.c | ||
| Kconfig | ||
| kvm_cache_regs.h | ||
| kvm_emulate.h | ||
| kvm_onhyperv.c | ||
| kvm_onhyperv.h | ||
| lapic.c | ||
| lapic.h | ||
| Makefile | ||
| mmu.h | ||
| mtrr.c | ||
| pmu.c | ||
| pmu.h | ||
| reverse_cpuid.h | ||
| trace.h | ||
| tss.h | ||
| x86.c | ||
| x86.h | ||
| xen.c | ||
| xen.h | ||