Hi Fred --
I understand your pain. I too wasted time building and
testing bits with the code turned on. However:
1) It is not uncommon in the open source community for the
needs of publicly-available machines to take precedence
over the needs of unreleased future machines.
2) It is not uncommon in the open source community for a
unreleased future machine to require different config
files than the defaults.
3) This specific code that is failing is not even needed
on publicly-available machines. It is not uncommon in
the open source community to refuse patches that are
only needed for unreleased future machines.
That said, I understand that your team as well as other
Xen developers are primarily using these future machines
for development and testing, so let me suggest a compromise:
Is there a way to dynamically test early in boot to determine
if this machine has split I-D caches? If so, you could provide
a patch that sets a global or cpu variable appropriately and
changes the compile-time ifdef to a run-time if test.
Dan
P.S. Thinking about this makes me realize.. the pal cache flush
code may be inadequate anyway when we get to SMP-guest support
because the stale mapping may be on another processor.
> -----Original Message-----
> From: Yang, Fred [mailto:fred.yang@xxxxxxxxx]
> Sent: Thursday, December 22, 2005 9:15 AM
> To: Magenheimer, Dan (HP Labs Fort Collins); Xu, Anthony;
> Tian, Kevin; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: CONFIG_IA64_SPLIT_CACHE was: [Xen-ia64-devel]
> Console problem on domU on tip?
>
> Dan,
>
> We spent long time to track down Cset#8383 yesterday, and now
> the current identified issue is I/Dcache patch was not turned
> on in the default built! Hope other community members won't
> hit this problem again.
>
> From the discussion, it is definitely the issue on the
> specific HP box on accessing PAL call. To be the correct
> approach, we should definitely track it down to find out the
> potential implementation or platform issue.
>
> Hope you can track this down ASAP to remove this hurdle.
>
> -Fred
>
> Magenheimer, Dan (HP Labs Fort Collins) wrote:
> > With CONFIG_IA64_SPLIT_CACHE on, a new user may encounter
> > the problem on a shipping machine and the symptom is that
> > the machine immediately crashes when a domU is launched.
> >
> > With CONFIG_IA64_SPLIT_CACHE off, a developer may encounter
> > a different problem on an unreleased machine.
> >
> > I know that you are focused primarily on the unreleased machine,
> > but in this case, I think we should be cautious for the new user
> > as the developer knows to change the option when running
> > on the unreleased machine.
> >
> > I will spend some more time on this when I have a chance.
> > I think it is a real bug (probably PAL accessing some address
> > which isn't pinned) that occurs only on some boxes due
> > to some factor like memory configuration.
> >
> > Thanks,
> > Dan
> >
> > P.S. The debug output just before the crash was:
> > ia64_fault: General Exception: IA-64 Reserved Register/Field fault
> > (data access): reflecting
> >
> >> -----Original Message-----
> >> From: Yang, Fred [mailto:fred.yang@xxxxxxxxx]
> >> Sent: Wednesday, December 21, 2005 10:34 PM
> >> To: Magenheimer, Dan (HP Labs Fort Collins); Xu, Anthony;
> >> Tian, Kevin; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >> Subject: CONFIG_IA64_SPLIT_CACHE was: [Xen-ia64-devel]
> >> Console problem on domU on tip?
> >>
> >> Dan,
> >>
> >> Can we suggest to always turn on #CONFIG_IA64_SPLIT_CACHE as
> >> the default build configuration. People may not be aware of
> >> this build flag and miss it one each new build.
> >>
> >> All the newer generation ia64 processors will come with
> >> splitted I/Dcache as discussed in the previous mail thread
> >> and it is documented in the Itanium architectur of possible
> >> splitted cache for future implementation. With default
> >> turning off, it is a potential bugs for all Tiger4 systems
> >> using for daily development and future platforms to come.
> >>
> >> It is also indicated through your mail, it is only HP rx2620
> >> system has issue and not the other HP boxes. Can you track
> >> down this issue? Rather than put a kludge for rx2620 box?
> >>
> >> Thanks,
> >>
> >> -Fred
> >>
> >>
> >> Magenheimer, Dan (HP Labs Fort Collins) wrote:
> >>> Committed (but without removal of ifdefs until we
> >>> track down this problem).
> >>>
> >>>> -----Original Message-----
> >>>> From: Xu, Anthony [mailto:anthony.xu@xxxxxxxxx]
> >>>> Sent: Monday, December 19, 2005 7:15 PM
> >>>> To: Magenheimer, Dan (HP Labs Fort Collins); Tian, Kevin;
> >>>> xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >>>> Subject: RE: [Xen-ia64-devel] Console problem on domU on tip?
> >>>>
> >>>> I guest maybe the firmware on your machine doesn't implement
> >>>> this pal call due to there is no split I/D cache at that
> >>>> time, so when you call this pal call, it will return
> >>>> PAL_STATUS_UNIMPLEMENTED, Could you please turn on
> >>>> CONFIG_IA64_SPLIT_CACHE and try this new patch to see
> >>>> whether your machine can boot domain0?
> >>>> If this patch works, could you please remove all
> >>>> CONFIG_IA64_SPLIT_CACHE macro?
> >>>>
> >>>> Thanks
> >>>> -Anthony
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: Magenheimer, Dan (HP Labs Fort Collins)
> >>>> [mailto:dan.magenheimer@xxxxxx]
> >>>>> Sent: 2005年12月19日 23:48
> >>>>> To: Xu, Anthony; Tian, Kevin; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >>>>> Subject: RE: [Xen-ia64-devel] Console problem on domU on tip?
> >>>>>
> >>>>> I have been distracted tracking another bug...
> >>>>>
> >>>>> Here's where I got:
> >>>>>
> >>>>> The machine is a new (April 2005) HP rx2620 so it is
> >>>>> not old firmware. I can't reproduce it on a machine
> >>>>> with an ITP (which does have older firmware).
> >>>>>
> >>>>> This PAL call is never used in Linux, though there is a
> >>>>> routine coded for it. It is the only
> >>>>> PAL call coded in Linux that occurs with psr.ic off.
> >>>>>
> >>>>> The crash I am seeing occurs either during the PAL call or
> >>>>> immediately upon return.
> >>>>>
> >>>>> Is it OK to
> >>>>>
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: Xu, Anthony [mailto:anthony.xu@xxxxxxxxx]
> >>>>>> Sent: Monday, December 19, 2005 2:02 AM
> >>>>>> To: Tian, Kevin; Magenheimer, Dan (HP Labs Fort Collins);
> >>>>>> xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >>>>>> Subject: RE: [Xen-ia64-devel] Console problem on domU on tip?
> >>>>>>
> >>>>>> Dan,
> >>>>>> Have you got time to verify below discussion?
> >>>>>>
> >>>>>> Thanks
> >>>>>> -Anthony
> >>>>>>
> >>>>>>> -----Original Message-----
> >>>>>>> From: Tian, Kevin
> >>>>>>> Sent: 2005年12月16日 10:16
> >>>>>>> To: Xu, Anthony; 'Magenheimer, Dan (HP Labs Fort Collins)';
> >>>>>>> 'xen-ia64-devel@xxxxxxxxxxxxxxxxxxx'
> >>>>>>> Subject: RE: [Xen-ia64-devel] Console problem on domU on tip?
> >>>>>>>
> >>>>>>>> From: Xu, Anthony
> >>>>>>>> Sent: 2005年12月16日 9:54
> >>>>>>>>
> >>>>>>>>> Also, why panic if it fails?
> >>>>>>>>>
> >>>>>>>
> >>>>>>> Panic is not required here, and we could just print out a
> >>>>>>> warning message. Previously panic is kept there to help our
> >>>>>>> debug in early stage.
> >>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> Does the problem happen only on VTI? Or both VTI
> and non-VTI
> >>>>>>>>> on split-cache machines?
> >>>>>>>>
> >>>>>>>> Sometimes, it makes domain0 crash at the very
> beginning of the
> >>>>>>>> domain0 boot process, especially on MP machine.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Thanks
> >>>>>>>> -Anthony
> >>>>>>>
> >>>>>>> One complement is, that problem definitely exists on new
> >>>>>>> split-cache processors, for dom0/domU. For VTI domain, we have
> >>>>>>> logic within device model to ensure consistence.
> >>>>>>>
> >>>>>>> Thanks,
> >>>>>>> Kevin
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> -----Original Message-----
> >>>>>>>>> From: Magenheimer, Dan (HP Labs Fort Collins)
> >>>>>>>> [mailto:dan.magenheimer@xxxxxx]
> >>>>>>>>> Sent: 2005年12月16日 1:39
> >>>>>>>>> To: Tian, Kevin; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >>>>>>>>> Cc: Xu, Anthony
> >>>>>>>>> Subject: RE: [Xen-ia64-devel] Console problem on
> domU on tip?
> >>>>>>>>>
> >>>>>>>>>>> Is this code fragment necessary for VTI to boot domU
> >>>>>>>>>>> or is it OK to remove?
> >>>>>>>>>>
> >>>>>>>>>> The comment is inaccurate and it should be
> domU. That I/D
> >>>>>>>>>> cache sync step is mandatory to boot domU on new IA64
> >>>>>>>>>> processor which has split L2 I/D cache. If without such I/D
> >>>>>>>>>> cache sync, control panel loads domU's kernel image which
> >>>>>>>>>> only affects D side cache. If there're some stale entry on
> >>>>>>>>>> I-side cache within same range of dom0 image, people will
> >>>>>>>>>> see machine going weird.
> >>>>>>>>>
> >>>>>>>>> I don't understand... how can there be stale entries in the
> >>>>>>>>> I-cache? The instructions have just been written to memory
> >>>>>>>>> (through D-cache) and no instructions in this
> domain have yet
> >>>>>>>>> been executed. I do see that the D-cache needs to be flushed
> >>>>>>>>> so that memory is coherent but are there better ways to do
> >>>>>>>>> that without a pal call?
> >>>>>>>>>
> >>>>>>>>>> Normally I/D cache sync shouldn't force any problem.
> >>>>>>>>>> Possibly there's some problem with the pal calling code,
> >>>>>>>>>> like incorrect ITLB mapping for pal or similar issue...
> >>>>>>>>>
> >>>>>>>>> Although the ia64_pal_cache_flush routine is defined in
> >>>>>>>>> linux's pal.h, it doesn't appear to be used
> anywhere in Linux
> >>>>>>>>> so there is no use model to copy. I suspect there is some
> >>>>>>>>> use model for the call that we don't understand, for example
> >>>>>>>>> maybe it should only be called with physical &progress? It
> >>>>>>>>> definitely fails every time on one of my (newer)
> machines and
> >>>>>>>>> disabling the pal call makes the problem go away.
> >>>>>>>>>
> >>>>>>>>>> Though it's intermittent, please
> >>>>>>>>>> keep this code
> >>>>>>>>>> there for correctness.
> >>>>>>>>>
> >>>>>>>>> Since the call is definitely failing under some
> circumstances
> >>>>>>>>> that we don't understand, I'm inclined to at least put the
> >>>>>>>>> code in an #ifdef CONFIG_SPLIT_CACHE
> >>>>>>>>>
> >>>>>>>>> Does the problem happen only on VTI? Or both VTI
> and non-VTI
> >>>>>>>>> on split-cache machines?
> >>>>>>>>>
> >>>>>>>>> Thanks,
> >>>>>>>>> Dan
> >>>>>>>>>
> >>>>>>>>> P.S. I tried Anthony's patch (which moves the PAL call after
> >>>>>>>>> new_thread()) but it still crashes.
>
>
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