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

> >>> On 12.06.14 at 03:28, <songtaox.liu@xxxxxxxxx> wrote:
> >> 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]


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