[libvirt] [[PATCH v2] 0/4] try harder to get dest qemu errors on migation

[Jiri Denemark]

On Thu, Oct 06, 2016 at 10:23:05 +0300, Nikolay Shirokovskiy wrote:
> 
> 
> On 05.10.2016 18:13, Peter Krempa wrote:
> > On Mon, Sep 12, 2016 at 17:34:39 +0300, Nikolay Shirokovskiy wrote:
> >> Hi, all.
> >>
> >>   In case migration fails due to destination qemu exits unexpectedly user
> >> recevies the qemu log in the error message. Unfortunately log is truncated and
> >> the most interesting part is missed (below is the example of such a log [1]).
> >>
> >> Actually for the most cases the first patch will be enough to fix the issue.
> >> Originally I thought the problem is qemu logging and reading the log are not in
> >> sync (which is true) so I tried to fix it as well in the next patches.
> >>
> >> * diff from v1:
> >>
> >> 1. split changes to libvirtd and virtlogd to different patches
> >> 2. split virtlogd patch further
> >> 3. simplify handling eofs and hangups in draining function
> >>
> >> [1] log example:
> >>
> >> CPU Reset (CPU 0)
> >> EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000000
> >> ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
> >> EIP=00000000 EFL=00000000 [-------] CPL=0 II=0 A20=0 SMM=0 HLT=0
> >> ES =0000 00000000 00000000 00000000
> >> CS =0000 00000000 00000000 00000000
> >> SS =0000 00000000 00000000 00000000
> >> DS =0000 00000000 00000000 00000000
> >> FS =0000 00000000 00000000 00000000
> >> GS =0000 00000000 00000000 00000000
> >> LDT=0000 00000000 00000000 00000000
> >> TR =0000 00000000 00000000 00000000
> >> GDT=     00000000 00000000
> >> IDT=     00000000 00000000
> >> CR0=00000000 CR2=00000000 CR3=00000000 CR4=00000000
> >> DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000 
> >> DR6=0000000000000000 DR7=0000000000000000
> >> CCS=00000000 CCD=00000000 CCO=DYNAMIC 
> >> EFER=0000000000000000
> >> FCW=0000 FSW=0000 [ST=0] FTW=ff MXCSR=00000000
> >> FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
> >> FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
> >> FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
> >> FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
> >> XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
> >> XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
> >> XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
> >> XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000
> >> CPU Reset (CPU 1)
> >> EAX=00000000 EBX=00000000 ECX=00000000 EDX=000206a1
> >> ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
> >> EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
> >> ES =0000 00000000 0000ffff 00009300
> >> CS =f000 ffff0000 0000ffff 00009b00
> >> SS =0000 00000000 0000ffff 00009300
> >> DS =0000 00000000 0000ffff 00009300
> >> FS =0000 00000000 0000ffff 00009300
> >> GS =0000 00000000 0000ffff 00009300
> >> LDT=0000 00000000 0000ffff 00008200
> >> TR =0000 00000000 0000ffff 00008b00
> >> GDT=     00000000 0000ffff
> >> IDT=     00000000 0000ffff
> >> CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
> >> DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000 
> >> DR6=00000000ffff0ff0 DR7=0000000000000400
> >> CCS=00000000 CCD=00000000 CCO=DYNAMIC 
> >> EFER=0000000000000000
> >> FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
> >> FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
> >> FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
> >> FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
> >> FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
> >> XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
> >> XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
> >> XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
> >> XMM06=00000000000000000000000000000000 XMM07=000
> >> qemu: terminating on signal 15 from pid 168133
> > 
> > I don't think that reporting all of the above is a good idea. We should
> > perhaps report at most two last lines.
> > 
> 
> We already report about half of this, this patch just removes random truncation.
> As to most two lines, AFAIU one can not say what part of this log will be
> useful for crash investigation.

Well, we're talking about error messages. And I doubt anyone would like
to see a 50 lines long error message. We have logs for investigating
crashes, the user should just get a reasonable message about why QEMU
died, i.e., showing something like the last two lines from the log looks
like a reasonable thing to do.

Jirka