[libre-riscv-dev] daily kan-ban update 09jun2020

Luke Kenneth Casson Leighton lkcl at lkcl.net
Wed Jun 10 14:16:18 BST 2020

> On Jun 9 2020, at 2:48 pm, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:

> Thank you, I appreciate the walkthrough and the story about going the
> old fashioned paper way. I thought that I had to do something in qemu
> itself, which would have been outside the bounds of this deductive
> reasoning process, as I have a tendency to get lost in forums and
> documentation when dealing with complex, always buggy to some extent,
> software like qemu.

hence the discussion in the bugreport (which you raised a couple days
ago?) about running actually against a POWER9 native.  skipping qemu
and running the programs directly, calling gdb on them.  exactly how
we'll do that, i have no idea yet, because it may require a huge
runtime, or possibly even virtualisation (to be able to run bare-metal
binaries directly).  have to see.

> So I wanted to see if we had prior art pertaining to
> qemu simulation. I think I should have taken the deductive reasoning
> about the codebase approch for my other questions.

it took me several years to work it out.

> I'm fighting my "aaah
> I don't understand," and with your reminder and guide here will be able
> to do so better next time.
> > powerpc64-linux-gnu-gdb -interpreter=mi
> > ~-data-list-register-names
> > ^done,register-names=
> >["r0","r1","r2","r3","r4","r5","r6","r7","r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18","r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29","r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9","f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20","f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31","pc","msr","cnd","lr","cnt","xer","fpscr","mq"
> > ah HA!  one of those is the condition register!
> Very cool and helpful.

i added them to test_sim.py - it causes test_sim.py unit tests to fail
(not your problem) because qemu defaults CR to 0x20000002 at start-up.
we can "fix" that by initialising the simulator CR to the same value.

> I think I over-stressed my self while working on
> the presentation yesterday, which has caused me to inadvertantly 'take'
> today off.

been there... :)

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