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

[Janosch Frank <frankja@linux.ibm.com>]

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?

> 
>>   	$(RM) $(@:.elf=.aux.o)
>>   	@chmod a-x $@
>>   
>> @@ -93,7 +115,7 @@ FLATLIBS = $(libcflat)
>>   	$(GENPROTIMG) --host-key-document $(HOST_KEY_DOCUMENT) --no-verify --image $< -o $@
>>   
>>   arch_clean: asm_offsets_clean
>> -	$(RM) $(TEST_DIR)/*.{o,elf,bin} $(TEST_DIR)/.*.d lib/s390x/.*.d
>> +	$(RM) $(TEST_DIR)/*.{o,elf,bin} $(SNIPPET_DIR)/c/*.{o,elf,bin,gbin} $(SNIPPET_DIR)/.*.d $(TEST_DIR)/.*.d lib/s390x/.*.d
>>   
>>   generated-files = $(asm-offsets)
>>   $(tests:.elf=.o) $(asmlib) $(cflatobjs): $(generated-files)
>> diff --git a/s390x/snippets/c/cstart.S b/s390x/snippets/c/cstart.S
>> new file mode 100644
>> index 00000000..02a3338b
>> --- /dev/null
>> +++ b/s390x/snippets/c/cstart.S
>> @@ -0,0 +1,13 @@
>> +#include <asm/sigp.h>
>> +
>> +.section .init
>> +	.globl start
>> +start:
>> +	/* XOR all registers with themselves to clear them fully. */
>> +	.irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
>> +	xgr \i,\i
>> +	.endr
>> +	/* 0x3000 is the stack page for now */
>> +	lghi	%r15, 0x4000
>> +	brasl	%r14, main
>> +	sigp    %r1, %r0, SIGP_STOP
> 
> I think you should clear r0 before using it here?

Right. will fix

> 
>   Thomas
>