Ingo Molnar wrote: > * Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > > Paolo Bonzini (11): > > Merge branch 'kvm-async-pf-int' into HEAD > > kvmtool broke in this merge window, hanging during bootup right after CPU bringup: > > [ 1.289404] #63 > [ 0.012468] kvm-clock: cpu 63, msr 6ff69fc1, secondary cpu clock > [ 0.012468] [Firmware Bug]: CPU63: APIC id mismatch. Firmware: 3f APIC: 14 > [ 1.302320] kvm-guest: KVM setup async PF for cpu 63 > [ 1.302320] kvm-guest: stealtime: cpu 63, msr 1379d7600 > > Eventually trigger an RCU stall warning: > > [ 22.302392] rcu: INFO: rcu_sched detected stalls on CPUs/tasks: > [ 22.302392] rcu: 1-...!: (68 GPs behind) idle=00c/0/0x0 softirq=0/0 fqs=0 (false positive?) > > I've bisected this down to the above merge commit. The individual commit: > > b1d405751cd5: ("KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery") > > appears to be working fine standalone. > > I'm using x86-64 defconfig+kvmconfig on SVM. Can send more info on request. > > The kvmtool.git commit I've tested is 90b2d3adadf2. Looks a lot like the lack of APIC EOI issue that Vitaly reported[*]. --- arch/x86/kernel/kvm.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index d45f34cbe1ef..9663ba31347c 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -271,6 +271,8 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_kvm_asyncpf_interrupt) struct pt_regs *old_regs = set_irq_regs(regs); u32 token; + ack_APIC_irq(); + inc_irq_stat(irq_hv_callback_count); if (__this_cpu_read(apf_reason.enabled)) { -- [*] https://lkml.kernel.org/r/20200908135350.355053-1-vkuznets@xxxxxxxxxx