MSR_SPE - being turned off...

[Morrison, Tom]

I'm sorry I forgot to put that, this issue was found with our 
currently running kernel 2.6.23.final (what comes with the 
Freescale LTIB BSP package dated 05/23/2009). 

I am sorry if I don't understand your statement that the SMP might
be broken on this kernel, because I tried to analyze the kernel that 
came with the latest BSP LTIB [ackage from Freescale (dated 12/18/2009 
(where we got the 4.2.171 compiler from)), and the associated 'switch 
context' code is exactly the same. Unfortunately, I have not started 
the process of porting my current platform's BSP to this new kernel - 
otherwise, I would have done the test on that platform (this also 
requires a new version of u-boot in order to test correctly))..

I may have mis-interpreted something and/or I am sure I don't 
understand everything about the SMP resource management (and 
associated SPE management), so thank you for any insight you 
may have on this front...

Tom

>> -----Original Message-----
>> From: Kumar Gala [mailto:galak at kernel.crashing.org]
>> Sent: Wednesday, May 06, 2009 8:32 AM
>> To: Morrison, Tom
>> Cc: Michael Neuling; linuxppc-dev at ozlabs.org
>> Subject: Re: MSR_SPE - being turned off...
>> 
>> 
>> On May 6, 2009, at 3:31 AM, Morrison, Tom wrote:
>> 
>> > Kumar,
>> >
>> > What about the case of a context switch (i.e.: when things are
setup
>> > in registers for the SPE, but then a context switch happens before
>> > the SPE is executed)?
>> 
>> context switches will be fine.  What we normally do is keep track of
>> which user app used SPE last and when some other app needs it we
clear
>> MSR_SPE for the old app, save its registers.  Than we load up the
>> registers for the new app and set MSR_SPE.  When the old app context
>> switches in it will get an SPE unavail exception at the point it
>> executes its next SPE insn and we will repeat the process.
>> 
>> > As to load_up_spe & give_up_spe, it was pointed out to me tonight
by
>> > a co-worker
>> > to look at how things are saved in those routines, I definitely
will
>> > look at this again,
c>> > and see how it is done...
>> >
>> > This is happening for us on an 8572 SMP. We are trying to get it to
>> > happen
>> > on 8548 (and single core 8572), but we haven't been able to push
>> > this part
>> > of the application as hard as it is being pushed on 8572...but we
>> > will keep trying....
>> 
>> Again, what kernel version for 8572?  Its possible old SMP kernels
are
>> broken on 8572.
>> 
>> - k
>> 
>> > ________________________________
>> >
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