[SLOF] [PATCH 3/4] fbuffer: Implement MRMOVE as an accelerated primitive

Thomas Huth thuth at redhat.com
Wed Sep 9 21:30:39 AEST 2015

On 09/09/15 13:05, Nikunj A Dadhania wrote:
> Thomas Huth <thuth at redhat.com> writes:
>> On 09/09/15 08:45, Nikunj A Dadhania wrote:
>>> Thomas Huth <thuth at redhat.com> writes:
>>>> On 03/08/15 17:53, Thomas Huth wrote:
>>>>> On 03/08/15 12:37, Nikunj A Dadhania wrote:
>>>>>> Thomas Huth <thuth at redhat.com> writes:
>>>>>>> The character drawing function fb8-draw-character uses "mrmove"
>>>>>>> (which moves main memory contents to IO memory) to copy the data
>>>>>>> of the character from main memory to the frame buffer. However,
>>>>>>> the current implementation of "mrmove"  performs quite badly on
>>>>>>> board-qemu since it triggers a hypercall for each memory access
>>>>>>> (e.g. for each 8 bytes that are transfered).
>>>>>>> But since the KVMPPC_H_LOGICAL_MEMOP hypercall can transfer bigger
>>>>>>> regions at once, we can accelerate the character drawing quite a
>>>>>>> bit by simply mapping the "mrmove" to the same macro that is
>>>>>>> already used for the "rmove". For keeping board-js2x in sync,
>>>>>>> this patch also transforms the "mrmove" for js2x into primitives.
>>>>>>> Signed-off-by: Thomas Huth <thuth at redhat.com>
>>>>>> I dont have a js2x handy, did you test this on js2x?
>>>>> No, sorry, unfortunately, I also was not able to test this on js2x yet.
>>>>> I still have a YDL PowerStation somewhere in a corner of my flat, but
>>>>> it's currently not set up ... will do that one day when I got enough
>>>>> spare time again, but that won't happen within the next few weeks (KVM
>>>>> forum's ahead!). So if there are problems, I'll fix them up as soon as I
>>>>> got the PowerStation running again (and I guess there might be other
>>>>> problems, too, since board-js2x hardly got any testing within the last
>>>>> months/years, I think).
>>>> FWIW, I've recently dusted off my PowerStation and gave it a try...
>>>> the HEAD of the SLOF master branch is unfortunately quite broken on js2x
>>>> nowadays (I'll try to send some first fixes later), but I was able to
>>>> cherry-pick the fbuffer acceleration patches to an older level of SLOF
>>>> from 2012 which was still working nicely.
>>> TCG seem to be broken with this new series, git bisect pointed to:
>>> 59a135e fbuffer: Implement MRMOVE as an accelerated primitive
>>> I havent looked into detail of why its failing though.
>> It seems to work fine for me here (SLOF master and QEMU master
>> branch). Which version of QEMU did you use? 
> QEMU: fc04a73 Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20150908' into staging
> SLOF: 811277a version: update to 20150813
>> Which command line parameters?
>         ./ppc64-softmmu/qemu-system-ppc64 -machine pseries -m 2048  -serial stdio

I've just tried the very same versions, with the very same parameters,
and it is working nicely here! Very strange...

>         VNC server running on `'
> 	SLOF **********************************************************************
> 	QEMU Starting
> 	 Build Date = Sep  9 2015 16:30:15
> 	 FW Version = git-811277ac91f674a9
> 	 Press "s" to enter Open Firmware.
> 	Cannot open file : fbuffer.fs

Sounds like the boot_rom.bin / slof.bin maybe has not been built
correctly ... what do you get when you run:

strings boot_rom.bin | grep fbuffer.fs



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