Re: [Qemu-devel] E5-2620v2 - emulation stop error

Andrey Korolyov
2015-03-30T19:32:24Z

On Mon, Mar 30, 2015 at 9:56 PM, Radim Krčmář <rkrcmar@redhat.com> wrote:
> 2015-03-27 13:16+0300, Andrey Korolyov:
>> On Fri, Mar 27, 2015 at 12:03 AM, Bandan Das <bsd@redhat.com> wrote:
>> > Radim Krčmář <rkrcmar@redhat.com> writes:
>> >> I second Bandan -- checking that it reproduces on other machine would be
>> >> great for sanity :) (Although a bug in our APICv is far more likely.)
>> >
>> > If it's APICv related, a run without apicv enabled could give more hints.
>> >
>> > Your "devices not getting reset" hypothesis makes the most sense to me,
>> > maybe the timer vector in the error message is just one part of
>> > the whole story. Another misbehaving interrupt from the dark comes in at the
>> > same time and leads to a double fault.
>>
>> Default trace (APICv enabled, first reboot introduced the issue):
>> http://xdel.ru/downloads/kvm-e5v2-issue/hanged-reboot-apic-on.dat.gz
>
> The relevant part is here,
> prefixed with "qemu-system-x86-4180 [002] 697.111550:"
>
> kvm_exit: reason CR_ACCESS rip 0xd272 info 0 0
> kvm_cr: cr_write 0 = 0x10
> kvm_mmu_get_page: existing sp gfn 0 0/4 q0 direct --- !pge !nxe root 0 sync
> kvm_entry: vcpu 0
> kvm_emulate_insn: f0000:d275: ea 7a d2 00 f0
> kvm_emulate_insn: f0000:d27a: 2e 0f 01 1e f0 6c
> kvm_emulate_insn: f0000:d280: 31 c0
> kvm_emulate_insn: f0000:d282: 8e e0
> kvm_emulate_insn: f0000:d284: 8e e8
> kvm_emulate_insn: f0000:d286: 8e c0
> kvm_emulate_insn: f0000:d288: 8e d8
> kvm_emulate_insn: f0000:d28a: 8e d0
> kvm_entry: vcpu 0
> kvm_exit: reason EXTERNAL_INTERRUPT rip 0xd28f info 0 800000f6
> kvm_entry: vcpu 0
> kvm_exit: reason EPT_VIOLATION rip 0x8dd0 info 184 0
> kvm_page_fault: address f8dd0 error_code 184
> kvm_entry: vcpu 0
> kvm_exit: reason EXTERNAL_INTERRUPT rip 0x8dd0 info 0 800000f6
> kvm_entry: vcpu 0
> kvm_exit: reason EPT_VIOLATION rip 0x76d6 info 184 0
> kvm_page_fault: address f76d6 error_code 184
> kvm_entry: vcpu 0
> kvm_exit: reason EXTERNAL_INTERRUPT rip 0x76d6 info 0 800000f6
> kvm_entry: vcpu 0
> kvm_exit: reason PENDING_INTERRUPT rip 0xd331 info 0 0
> kvm_inj_virq: irq 8
> kvm_entry: vcpu 0
> kvm_exit: reason EXTERNAL_INTERRUPT rip 0xfea5 info 0 800000f6
> kvm_entry: vcpu 0
> kvm_exit: reason EPT_VIOLATION rip 0xfea5 info 184 0
> kvm_page_fault: address ffea5 error_code 184
> kvm_entry: vcpu 0
> kvm_exit: reason EXTERNAL_INTERRUPT rip 0xfea5 info 0 800000f6
> kvm_entry: vcpu 0
> kvm_exit: reason EPT_VIOLATION rip 0xe990 info 184 0
> kvm_page_fault: address fe990 error_code 184
> kvm_entry: vcpu 0
> kvm_exit: reason EXTERNAL_INTERRUPT rip 0xe990 info 0 800000f6
> kvm_entry: vcpu 0
> kvm_exit: reason EXCEPTION_NMI rip 0xd334 info 0 80000b0d
> kvm_userspace_exit: reason KVM_EXIT_INTERNAL_ERROR (17)
>
>> Trace without APICv (three reboots, just to make sure to hit the
>> problematic condition of supposed DF, as it still have not one hundred
>> percent reproducibility):
>> http://xdel.ru/downloads/kvm-e5v2-issue/apic-off.dat.gz
>
> The trace here contains a well matching excerpt, just instead of the
> EXCEPTION_NMI, it does
>
> 169.905098: kvm_exit: reason EPT_VIOLATION rip 0xd334 info 181 0
> 169.905102: kvm_page_fault: address feffd066 error_code 181
>
> and works. Page fault says we tried to read 0xfeffd066 -- probably IOPB
> of TSS. (I guess it is pre-fetch for following IO instruction.)
>
> Nothing strikes me when looking at it, but some APICv boots don't fail,
> so it would be interesting to compare them ... hosts's 0xf6 interrupt
> (IRQ_WORK_VECTOR) is a possible source of races. (We could look more
> closely. It is fired too often for my liking as well.)

Thanks Radim, http://xdel.ru/downloads/kvm-e5v2-issue/no-fail-with-apicv.dat.gz

(missed right button in mailer previously)

The related bits looks the same as with enable_apicv=0 for me.