Re: [Xen-devel] [PATCH] x86/EPT: flush cache when (potentially) limiting cachability

["Liu, SongtaoX" <songtaox.liu@xxxxxxxxx>]

> >> >> From: Jan Beulich [mailto:jbeulich@xxxxxxxx]
> >> >> >>> "Liu, SongtaoX" <songtaox.liu@xxxxxxxxx> 05/30/14 9:35 AM >>>
> >> >> >Sorry to update.
> >> >> >The bug refers to
> >> >> http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1887.
> >> >> >L2 guest vnc console hangs at black screen with cursor flashing
> >> >> >at the top
> >> > left
> >> >> corner.
> >> >> >After several minutes, the Seabios screen shows up, but the
> >> >> >screen still
> >> > flush
> >> >> slowly, the guest could not boot up.
> >> >>
> >> >> That would then indeed be an indication of excessive flushes. I.e.
> >> >> you may
> >> > want
> >> >> to simply track down which one (and why) gets triggered too often.
> >> >>
> >> > How to get that information? It is hard for me to do it since I am
> >> > not a Xen expert. But if you can provide a patch help to debug, I
> >> > would happy
> > to
> >> do it.
> >>
> >> The original patch makes quite clear where to put the
> >> instrumentation; I'm attaching a patch anyway for you to try. This
> >> (obviously) is against the
> > current
> >> staging tree - while it ought to apply fine on master, it certainly
> >> won't
> > apply on
> >> 4.4 or older without adjustments.
> >>
> > Env: Xen.git, master, commit:
> > 7f8d8abcf6dfb85fae591a547b24f9b27d92272c, with your patch,
> > L2 guest with "hap=1", after creating the L2, "xl dmesg" in L0 shows:
> > (XEN) chg[000020] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[000040] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[000080] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[000100] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[000200] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[000400] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[000800] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[001000] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[002000] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[004000] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[008000] d1 [hvm_set_guest_pat+0xad/0xb9]
> > (XEN) chg[008000] d1 [hvm_set_guest_pat+0xad/0xb9]
> 
> This looks like it's not really a proper part of the log (the last two lines 
> being
> duplicated). Which underlines that you should supply
> (attach!) full logs rather than decide on your own which part(s) might be
> relevant.
> 
> _Assuming_ the tail above really is the tail of the log, I can't see why the 
> guest
> wouldn't come up: 32k cache flushes aren't the end of the world. There ought
> to be something else...
> 
Sorry, it's my mistake, the last line should be " (XEN) chg[010000] d1 
[hvm_set_guest_pat+0xad/0xb9]".
Full L0 serial log as attached, it was from L0 boot to L2 guest creation.
After creating L2, it takes nearly 15 minutes to print the last line of " (XEN) 
chg[040000] d1 [hvm_set_guest_pat+0xad/0xb9]". 
No other logs printed out in 20 minutes.

Regards
Songtao

Attachment: xen-nested-serial.log
Description: xen-nested-serial.log

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