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
