* Christopherson, Sean J <sean.j.christopherson@xxxxxxxxx> wrote:
> 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
Yep, this does the trick, thanks!
Tested-by: Ingo Molnar <mingo@xxxxxxxxxx>
Ingo
