CPU: Fix switching in of x86 CPU with interrupt and TLB ports

Information
Submitter:	Andreas Hansson
Repository:	gem5
Branch:	default
Bugs:
Depends On:
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Groups:	Default
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Description

CPU: Fix switching in of x86 CPU with interrupt and TLB ports

This patch fixes the, currently broken, switching of CPUs for x86 by
ensuring that the interrupt device does not initialise the ports if
the CPU is not connected, and also ensures that the TLB walker ports
of the new CPU are actually connected. To do the latter the getPort of
the TLB and TLB walker for x86 were added to override the BaseTLB that
returns NULL.

Testing Done

util/regress all passing (disregarding t1000 and eio)

Andreas, is it necessary to generate the interrupts object in case we know
that the cpu will take over the object from another cpu later?

Ankita Garg Feb. 24, 2012, 6:04 a.m. (Feb. 24, 2012, 6:04 a.m.)

I tried the patch, but I still hit the pio port not being connected issue. I tried the following commandline:

build/X86/gem5.opt configs/example/fs.py --cpu-type=detailed --kernel=x86_64-vmlinux-2.6.22.9 --caches -F 1000

...

command line: build/X86/gem5.opt configs/example/fs.py --cpu-type=detailed --kernel=x86_64-vmlinux-2.6.22.9 --caches -F 1000
warning: add_child('terminal'): child 'terminal' already has parent
Global frequency set at 1000000000000 ticks per second
      0: rtc: Real-time clock set to Sun Jan  1 00:00:00 2012
Listening for com_1 connection on port 3456
warn: Reading current count from inactive timer.
0: system.remote_gdb.listener: listening for remote gdb #0 on port 7000
panic: Pio port of system.switch_cpus.interrupts not connected to anything!
 @ cycle 0
[init:build/X86/dev/io_device.cc, line 69]
Memory Usage: 213616 KBytes
Program aborted at cycle 0
Aborted
....

Andreas Hansson Feb. 24, 2012, 5:19 p.m. (Feb. 24, 2012, 5:19 p.m.)

Nilay, this was merely the simplest fix I could create with my expertise of the ports/CPU. If someone that knows the CPU models better wants to make a stab at taking the interrups unit over then that is of course fine as well. 

Ankita, the command you suggest works fine with this patch applied to an updated repo. Could you please verify that everything is up to date, Pply the patch again and let me know the result. I've tried on two independent machines just to be sure and it runs fine.

Ali Saidi Feb. 25, 2012, 4:52 a.m. (Feb. 25, 2012, 4:52 a.m.)

Nilay,

I think we do want to change to only instantiating the object once. I've got a patch I can send you that starts down that path, but I didn't finish it. It works for the interrupt controller, but I think we want to do the same thing for the tlb and walker as well. There is a use case for changing out the CPU at run time ,but I don't think there is one to change the interrupt controller and tlb, so we should do a uniform thing for both. Could you take a look at making that happen?

Thanks,
Ali

Nilay Vaish Feb. 25, 2012, 8:46 a.m. (Feb. 25, 2012, 8:46 a.m.)
```
Sure, mail me the patch. I'll get it done.
```

Ship It!

Gabe Black Feb. 27, 2012, 11:40 a.m. (Feb. 27, 2012, 11:40 a.m.)

Uh, this really didn't look it was ready to ship. Ankita said it didn't fix her problem, and Nilay said he was going to write a new version.

Ali Saidi Feb. 27, 2012, 11:58 a.m. (Feb. 27, 2012, 11:58 a.m.)

It seems to fix the problem reported for me and we don't know how long it's going to take to get a  improved solution that fixes the interrupt, tlb, everything else for all the architectures. I'd prefer to commit this now so the functionality isn't broken in the head and then un-do it when a more complete fix is available. Thoughts?

Gabe Black Feb. 27, 2012, 3:56 p.m. (Feb. 27, 2012, 3:56 p.m.)

If it fixes the problem then sure, that makes sense. I'm curious why it didn't work for Ankita.

Andreas Hansson Feb. 27, 2012, 4:40 p.m. (Feb. 27, 2012, 4:40 p.m.)

I did ask Ankita to re-run everything with the patch as it definitely solves the problem on my side. Any news on this front, Ankita?

Nilay Vaish Feb. 27, 2012, 10:49 p.m. (Feb. 27, 2012, 10:49 p.m.)

I have posted two new patches, these combine the patch posted by Andreas and the one that
Ali emailed me.

You have a pending review.

Review Board 2.0.15

This change has been discarded.

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