Re: [Qemu-devel] [PATCH V8 2/4] tests/migration: Support cross compilation in generating boot header file

[Wei Huang <wehuang@redhat.com>]

----- Original Message -----
> From: "Andrew Jones" <drjones@redhat.com>
> To: "Wei Huang" <wei@redhat.com>
> Cc: qemu-devel@nongnu.org, lvivier@redhat.com, "peter maydell" <peter.maydell@linaro.org>, quintela@redhat.com,
> dgilbert@redhat.com
> Sent: Monday, September 3, 2018 6:26:39 AM
> Subject: Re: [Qemu-devel] [PATCH V8 2/4] tests/migration: Support cross compilation in generating boot header file
> 
> On Sat, Sep 01, 2018 at 01:11:13AM -0400, Wei Huang wrote:
> > Recently a new configure option, CROSS_CC_GUEST, was added to
> > $(TARGET)-softmmu/config-target.mak to support TCG-related tests. This
> > patch tries to leverage this option to support cross compilation when the
> > migration boot block file is being re-generated:
> > 
> >  * The x86_64 related files are moved to a new sub-dir (named ./x86_64).
> >  * A new top-layer Makefile is created in tests/migration/ directory.
> >    This Makefile searches and parses CROSS_CC_GUEST to generate
> >    CROSS_PREFIX.
> >    The CROSS_PREFIX, if available, is then passed to
> >    migration/$ARCH/Makefile.
> > 
> > Signed-off-by: Wei Huang <wei@redhat.com>
> > ---
> >  tests/migration-test.c                           |  2 +-
> >  tests/migration/Makefile                         | 43
> >  +++++++++++++-----------
> >  tests/migration/x86_64/Makefile                  | 22 ++++++++++++
> >  tests/migration/{ => x86_64}/x86-a-b-bootblock.S |  0
> >  tests/migration/{ => x86_64}/x86-a-b-bootblock.h |  8 ++---
> >  5 files changed, 50 insertions(+), 25 deletions(-)
> >  create mode 100644 tests/migration/x86_64/Makefile
> >  rename tests/migration/{ => x86_64}/x86-a-b-bootblock.S (100%)
> >  rename tests/migration/{ => x86_64}/x86-a-b-bootblock.h (93%)
> > 
> > diff --git a/tests/migration-test.c b/tests/migration-test.c
> > index 0e687b7..c4d79e9 100644
> > --- a/tests/migration-test.c
> > +++ b/tests/migration-test.c
> > @@ -83,7 +83,7 @@ static const char *tmpfs;
> >  /* A simple PC boot sector that modifies memory (1-100MB) quickly
> >   * outputting a 'B' every so often if it's still running.
> >   */
> > -#include "tests/migration/x86-a-b-bootblock.h"
> > +#include "tests/migration/x86_64/x86-a-b-bootblock.h"
> 
> Is x86-a-b-bootblock.h specific to x86_64, or both i386 and x86_64?
> I think we want the dir name to be i386 if it's the later. Also,
> we could drop the 'x86-' prefix from the filename, now that the
> directory identifies the arch.

Well, I can try it. But this will make the Makefile more complicated as we have to detect x86_64 compiler for i386 binary (most distros only ship x86_64 cross compiler).

> 
> >  
> >  static void init_bootfile_x86(const char *bootpath)
> >  {
> > diff --git a/tests/migration/Makefile b/tests/migration/Makefile
> > index 5d5fa07..1de480e 100644
> > --- a/tests/migration/Makefile
> > +++ b/tests/migration/Makefile
> > @@ -1,31 +1,34 @@
> > -# To specify cross compiler prefix, use CROSS_PREFIX=
> > -#   > make CROSS_PREFIX=x86_64-linux-gnu-
> > +#
> > +# Copyright (c) 2018 Red Hat, Inc. and/or its affiliates
> > +#
> > +# This work is licensed under the terms of the GNU GPL, version 2 or
> > later.
> > +# See the COPYING file in the top-level directory.
> > +#
> > +
> > +TARGET_LIST = x86_64
> > +
> > +SRC_PATH = ../..
> >  
> >  override define __note
> > -/* This file is automatically generated from
> > - * tests/migration/x86-a-b-bootblock.s, edit that and then run
> > - * tests/migration/rebuild-x86-bootblock.sh to update,
> > - * and then remember to send both in your patch submission.
> > +/* This file is automatically generated from the assembly file in
> > + * tests/migration/$@, edit that and then run "make all"
> 
> nit: /, edit that/. Edit that file/
> 
> > + * inside tests/migration to update, and then remember to send both
> > + * in your patch submission.
> nit: ^ the header and the assembler differences
> 
> >   */
> >  endef
> >  export __note
> >  
> > -.PHONY: all clean
> > -all: x86-a-b-bootblock.h
> > -
> > -x86-a-b-bootblock.h: x86.bootsect
> > -	echo "$$__note" > header.tmp
> > -	xxd -i $< | sed -e 's/.*int.*//' >> header.tmp
> > -	mv header.tmp $@
> > +parse-cross-prefix = $(subst gcc,,$(patsubst cc,gcc,$(patsubst
> > CROSS_CC_GUEST="%",%,$(shell grep "CROSS_CC_GUEST="
> > $(SRC_PATH)/$(1)-softmmu/config-target.mak))))
> > +gen-cross-prefix = $(patsubst %-,CROSS_PREFIX=%-,$(call
> > parse-cross-prefix,$(1)))
> >  
> > -x86.bootsect: x86.boot
> > -	dd if=$< of=$@ bs=256 count=2 skip=124
> > +.PHONY: all $(TARGET_LIST)
> >  
> > -x86.boot: x86.o
> > -	$(CROSS_PREFIX)objcopy -O binary $< $@
> > +all: $(TARGET_LIST)
> >  
> > -x86.o: x86-a-b-bootblock.S
> > -	$(CROSS_PREFIX)gcc -m32 -march=i486 -c $< -o $@
> > +$(TARGET_LIST):
> > +	$(MAKE) -C $@ $(call gen-cross-prefix,$@)
> >  
> >  clean:
> > -	@rm -rf *.boot *.o *.bootsect
> > +	for target in $(TARGET_LIST); do \
> > +		$(MAKE) -C $$target clean; \
> > +	done
> 
> The above seems overly complicated. Does the following work?
> 
> $(TARGET_LIST): CROSS_PREFIX=$(CROSS_CC_GUEST)
> $(TARGET_LIST):
> 	$(MAKE) -C $@

No, it doen't work for different reasons.

First, to have CROSS_CC_GUEST defined, we normally would use "-include" to include config-target.mak file. But the end result is, the CROSS_CC_GUEST only has the same definition for both architectures (due to make command's multi-iteration processing and include is processed first). Secondly, CROSS_CC_GUEST needs to be polished because it can be: i) not defined; ii) "cc" without prefix; or iii) used-define value. We can't use it directly.



> 
> 
> > diff --git a/tests/migration/x86_64/Makefile
> > b/tests/migration/x86_64/Makefile
> > new file mode 100644
> > index 0000000..6dc849f
> > --- /dev/null
> > +++ b/tests/migration/x86_64/Makefile
> > @@ -0,0 +1,22 @@
> > +# To specify cross compiler prefix, use CROSS_PREFIX=
> > +#   > make CROSS_PREFIX=x86_64-linux-gnu-
> > +
> > +.PHONY: all clean
> > +all: x86-a-b-bootblock.h
> > +
> > +x86-a-b-bootblock.h: x86.bootsect
> > +	echo "$$__note" > header.tmp
> > +	xxd -i $< | sed -e 's/.*int.*//' >> header.tmp
> > +	mv header.tmp $@
> > +
> > +x86.bootsect: x86.boot
> > +	dd if=$< of=$@ bs=256 count=2 skip=124
> > +
> > +x86.boot: x86.o
> > +	$(CROSS_PREFIX)objcopy -O binary $< $@
> > +
> > +x86.o: x86-a-b-bootblock.S
> > +	$(CROSS_PREFIX)gcc -m32 -march=i486 -c $< -o $@
> > +
> > +clean:
> > +	@rm -rf *.boot *.o *.bootsect
> > diff --git a/tests/migration/x86-a-b-bootblock.S
> > b/tests/migration/x86_64/x86-a-b-bootblock.S
> > similarity index 100%
> > rename from tests/migration/x86-a-b-bootblock.S
> > rename to tests/migration/x86_64/x86-a-b-bootblock.S
> > diff --git a/tests/migration/x86-a-b-bootblock.h
> > b/tests/migration/x86_64/x86-a-b-bootblock.h
> > similarity index 93%
> > rename from tests/migration/x86-a-b-bootblock.h
> > rename to tests/migration/x86_64/x86-a-b-bootblock.h
> > index 78a151f..73670ef 100644
> > --- a/tests/migration/x86-a-b-bootblock.h
> > +++ b/tests/migration/x86_64/x86-a-b-bootblock.h
> > @@ -1,7 +1,7 @@
> > -/* This file is automatically generated from
> > - * tests/migration/x86-a-b-bootblock.s, edit that and then run
> > - * tests/migration/rebuild-x86-bootblock.sh to update,
> > - * and then remember to send both in your patch submission.
> > +/* This file is automatically generated from the assembly file in
> > + * tests/migration/x86_64, edit that and then run "make all"
> > + * inside tests/migration to update, and then remember to send both
> > + * in your patch submission.
> >   */
> >  unsigned char x86_bootsect[] = {
> >    0xfa, 0x0f, 0x01, 0x16, 0x74, 0x7c, 0x66, 0xb8, 0x01, 0x00, 0x00, 0x00,
> > --
> > 1.8.3.1
> > 
> >
> 
> Thanks,
> drew
>