On Wed, Dec 13, 2023, Like Xu wrote: > > > On 13/12/2023 3:28 pm, Dongli Zhang wrote: > > Hi Like, > > > > On 12/5/23 19:20, Like Xu wrote: > > > From: Like Xu <likexu@xxxxxxxxxxx> > > > > > > Explicitly checking the source of external interrupt is indeed NMI and not > > > other types in the kvm_arch_pmi_in_guest(), which prevents perf-kvm false > > > positive samples generated in perf/core NMI mode after vm-exit but before > > > kvm_before_interrupt() from being incorrectly labelled as guest samples: > > > > About the before kvm_before_interrupt() ... > > > > > > > > # test: perf-record + cpu-cycles:HP (which collects host-only precise samples) > > > # Symbol Overhead sys usr guest sys guest usr > > > # ....................................... ........ ........ ........ ......... ......... > > > # > > > # Before: > > > [g] entry_SYSCALL_64 24.63% 0.00% 0.00% 24.63% 0.00% > > > [g] syscall_return_via_sysret 23.23% 0.00% 0.00% 23.23% 0.00% > > > [g] files_lookup_fd_raw 6.35% 0.00% 0.00% 6.35% 0.00% > > > # After: > > > [k] perf_adjust_freq_unthr_context 57.23% 57.23% 0.00% 0.00% 0.00% > > > [k] __vmx_vcpu_run 4.09% 4.09% 0.00% 0.00% 0.00% > > > [k] vmx_update_host_rsp 3.17% 3.17% 0.00% 0.00% 0.00% > > > > > > In the above case, perf records the samples labelled '[g]', the RIPs behind > > > the weird samples are actually being queried by perf_instruction_pointer() > > > after determining whether it's in GUEST state or not, and here's the issue: > > > > > > If vm-exit is caused by a non-NMI interrupt (such as hrtimer_interrupt) and > > > at least one PMU counter is enabled on host, the kvm_arch_pmi_in_guest() > > > will remain true (KVM_HANDLING_IRQ is set) until kvm_before_interrupt(). > > > > ... and here. > > > > Would you mind helping why kvm_arch_pmi_in_guest() remains true before > > *kvm_before_interrupt()*. > > > > According to the source code, the vcpu->arch.handling_intr_from_guest > > is set to non-zero only at kvm_before_interrupt(), and cleared at > > kvm_after_interrupt(). > > > > Or would you mean kvm_after_interrupt()? > > Oops, it should refer to kvm_after_interrupt() as the code fixed. Thank you. No need for another version if that's the only hiccup, I can fixup when applying.
