Re: [PATCH v6 1/8] xen: reuse x86 EFI stub functions for Arm

[Julien Grall <julien@xxxxxxx>]

Hi,

On 24/06/2022 08:18, Wei Chen wrote:
> > -----Original Message-----
> > From: Jan Beulich <jbeulich@xxxxxxxx>
> > Sent: 2022年6月23日 20:54
> > To: Wei Chen <Wei.Chen@xxxxxxx>
> > Cc: nd <nd@xxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>; Julien
> > Grall <julien@xxxxxxx>; Bertrand Marquis <Bertrand.Marquis@xxxxxxx>;
> > Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>; Andrew Cooper
> > <andrew.cooper3@xxxxxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>; Wei
> > Liu <wl@xxxxxxx>; Jiamei Xie <Jiamei.Xie@xxxxxxx>; xen-
> > devel@xxxxxxxxxxxxxxxxxxxx
> > Subject: Re: [PATCH v6 1/8] xen: reuse x86 EFI stub functions for Arm
> >
> > On 10.06.2022 07:53, Wei Chen wrote:
> > > --- a/xen/arch/arm/Makefile
> > > +++ b/xen/arch/arm/Makefile
> > > @@ -1,6 +1,5 @@
> > >   obj-$(CONFIG_ARM_32) += arm32/
> > >   obj-$(CONFIG_ARM_64) += arm64/
> > > -obj-$(CONFIG_ARM_64) += efi/
> > >   obj-$(CONFIG_ACPI) += acpi/
> > >   obj-$(CONFIG_HAS_PCI) += pci/
> > >   ifneq ($(CONFIG_NO_PLAT),y)
> > > @@ -20,6 +19,7 @@ obj-y += domain.o
> > >   obj-y += domain_build.init.o
> > >   obj-y += domctl.o
> > >   obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
> > > +obj-y += efi/
> > >   obj-y += gic.o
> > >   obj-y += gic-v2.o
> > >   obj-$(CONFIG_GICV3) += gic-v3.o
> > > --- a/xen/arch/arm/efi/Makefile
> > > +++ b/xen/arch/arm/efi/Makefile
> > > @@ -1,4 +1,12 @@
> > >   include $(srctree)/common/efi/efi-common.mk
> > >
> > > +ifeq ($(CONFIG_ARM_EFI),y)
> > >   obj-y += $(EFIOBJ-y)
> > >   obj-$(CONFIG_ACPI) +=  efi-dom0.init.o
> > > +else
> > > +# Add stub.o to EFIOBJ-y to re-use the clean-files in
> > > +# efi-common.mk. Otherwise the link of stub.c in arm/efi
> > > +# will not be cleaned in "make clean".
> > > +EFIOBJ-y += stub.o
> > > +obj-y += stub.o
> > > +endif
> > This has caused
> >
> > ld: warning: arch/arm/efi/built_in.o uses 2-byte wchar_t yet the output is
> > to use 4-byte wchar_t; use of wchar_t values across objects may fail
> >
> > for the 32-bit Arm build that I keep doing every once in a while, with
> > (if it matters) GNU ld 2.38. I guess you will want to consider building
> > all of Xen with -fshort-wchar, or to avoid building stub.c with that
> > option.
> Thanks for pointing this out. I will try to use -fshort-wchar for Arm32,
> if Arm maintainers agree.
Looking at the code we don't seem to build Xen arm64 with -fshort-wchar 
(aside the EFI files). So it is not entirely clear why we would want to 
use -fshort-wchar for arm32.
Cheers,

--
Julien Grall