Re: [kvm-unit-tests RFC 1/2] s390x: Add guest snippet support

[Thomas Huth <thuth@redhat.com>]

On 21/06/2021 16.42, Janosch Frank wrote:
> On 6/21/21 3:28 PM, Thomas Huth wrote:
>> On 21/06/2021 14.39, Janosch Frank wrote:
>>> On 6/21/21 2:32 PM, Thomas Huth wrote:
>>>> On 21/06/2021 14.19, Janosch Frank wrote:
>>>>> On 6/21/21 12:10 PM, Thomas Huth wrote:
>>>>>> On 20/05/2021 11.47, Janosch Frank wrote:
>>>>>>> Snippets can be used to easily write and run guest (SIE) tests.
>>>>>>> The snippet is linked into the test binaries and can therefore be
>>>>>>> accessed via a ptr.
>>>>>>>
>>>>>>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>>>>>>> ---
>>>>>>>      .gitignore                |  2 ++
>>>>>>>      s390x/Makefile            | 28 ++++++++++++++++++---
>>>>>>>      s390x/snippets/c/cstart.S | 13 ++++++++++
>>>>>>>      s390x/snippets/c/flat.lds | 51 +++++++++++++++++++++++++++++++++++++++
>>>>>>>      4 files changed, 91 insertions(+), 3 deletions(-)
>>>>>>>      create mode 100644 s390x/snippets/c/cstart.S
>>>>>>>      create mode 100644 s390x/snippets/c/flat.lds
>>>>>>>
>>>>>>> diff --git a/.gitignore b/.gitignore
>>>>>>> index 784cb2dd..29d3635b 100644
>>>>>>> --- a/.gitignore
>>>>>>> +++ b/.gitignore
>>>>>>> @@ -22,3 +22,5 @@ cscope.*
>>>>>>>      /api/dirty-log
>>>>>>>      /api/dirty-log-perf
>>>>>>>      /s390x/*.bin
>>>>>>> +/s390x/snippets/*/*.bin
>>>>>>> +/s390x/snippets/*/*.gbin
>>>>>>> diff --git a/s390x/Makefile b/s390x/Makefile
>>>>>>> index 8de926ab..fe267011 100644
>>>>>>> --- a/s390x/Makefile
>>>>>>> +++ b/s390x/Makefile
>>>>>>> @@ -75,11 +75,33 @@ OBJDIRS += lib/s390x
>>>>>>>      asmlib = $(TEST_DIR)/cstart64.o $(TEST_DIR)/cpu.o
>>>>>>>      
>>>>>>>      FLATLIBS = $(libcflat)
>>>>>>> -%.elf: %.o $(FLATLIBS) $(SRCDIR)/s390x/flat.lds $(asmlib)
>>>>>>> +
>>>>>>> +SNIPPET_DIR = $(TEST_DIR)/snippets
>>>>>>> +
>>>>>>> +# C snippets that need to be linked
>>>>>>> +snippets-c =
>>>>>>> +
>>>>>>> +# ASM snippets that are directly compiled and converted to a *.gbin
>>>>>>> +snippets-a =
>>>>>>
>>>>>> Could you please call this snippets-s instead of ...-a ? The -a suffix looks
>>>>>> like an archive to me otherwise.
>>>>>
>>>>> Sure
>>>>>
>>>>>>
>>>>>>> +snippets = $(snippets-a)$(snippets-c)
>>>>>>
>>>>>> Shouldn't there be a space between the two?
>>>>>
>>>>> Yes, already fixed that a long while ago
>>>>> I thought I had sent out a new version already, maybe that was an
>>>>> illusion as I can't seem to find it right now.
>>>>>
>>>>>>
>>>>>>> +snippets-o += $(patsubst %.gbin,%.o,$(snippets))
>>>>>>> +
>>>>>>> +$(snippets-a): $(snippets-o) $(FLATLIBS)
>>>>>>> +	$(OBJCOPY) -O binary $(patsubst %.gbin,%.o,$@) $@
>>>>>>> +	$(OBJCOPY) -I binary -O elf64-s390 -B "s390:64-bit" $@ $@
>>>>>>> +
>>>>>>> +$(snippets-c): $(snippets-o) $(SNIPPET_DIR)/c/cstart.o  $(FLATLIBS)
>>>>>>> +	$(CC) $(LDFLAGS) -o $@ -T $(SNIPPET_DIR)/c/flat.lds \
>>>>>>> +		$(filter %.o, $^) $(FLATLIBS)
>>>>>>> +	$(OBJCOPY) -O binary $@ $@
>>>>>>> +	$(OBJCOPY) -I binary -O elf64-s390 -B "s390:64-bit" $@ $@
>>>>>>> +
>>>>>>> +%.elf: $(snippets) %.o $(FLATLIBS) $(SRCDIR)/s390x/flat.lds $(asmlib)
>>>>>>>      	$(CC) $(CFLAGS) -c -o $(@:.elf=.aux.o) \
>>>>>>>      		$(SRCDIR)/lib/auxinfo.c -DPROGNAME=\"$@\"
>>>>>>>      	$(CC) $(LDFLAGS) -o $@ -T $(SRCDIR)/s390x/flat.lds \
>>>>>>> -		$(filter %.o, $^) $(FLATLIBS) $(@:.elf=.aux.o)
>>>>>>> +		$(filter %.o, $^) $(FLATLIBS) $(snippets) $(@:.elf=.aux.o)
>>>>>>
>>>>>> Does this link the snippets into all elf files? ... wouldn't it be better to
>>>>>> restrict it somehow to the files that really need them?
>>>>>
>>>>> Yes it does.
>>>>> I'd like to avoid having to specify a makefile rule for every test that
>>>>> uses snippets as we already have more than the mvpg one in the queue.
>>>>>
>>>>> So I'm having Steffen looking into a solution for this problem. My first
>>>>> idea was to bring the used snippets into the unittests.cfg but I
>>>>> disliked that we then would have compile instructions in another file.
>>>>> Maybe there's a way to include that into the makefile in a clever way?
>>>>
>>>> I haven't tried, but maybe you could replace the $(snippets) in the last
>>>> line with
>>>>
>>>>     $(wildcard snippets/$@.gbin)
>>>>
>>>> or something similar?
>>>
>>> That starts falling apart when multiple tests use the same snippet, no?
>>
>> That's true ... Maybe something like:
>>
>>    $(filter %.gbin,$^)
> 
> That filters all files that are not gbins from the prereqs, right?
> In what way is that different to linking all the snippets? After all
> they are currently a prereq for %.elf or am I missing something here?

Sorry, I meant we could then add the prereqs manually for each tests that 
require it, e.g. add a single line like:

mvpg-sie.elf: snippets/mvpg.gbin

(without specifying a rule, just the dependency)

... not sure whether that works, though...

  Thomas