Re: [Xen-devel] how to disable build of pv-shim?

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.05.19 at 11:23, <wei.liu2@xxxxxxxxxx> wrote:
> On Tue, May 14, 2019 at 10:55:18AM +0200, Roger Pau Monné wrote:
>> On Mon, May 13, 2019 at 04:28:12PM +0100, Wei Liu wrote:
>> > On Mon, May 13, 2019 at 05:20:05PM +0200, Roger Pau Monné wrote:
>> > > On Mon, May 13, 2019 at 04:53:21PM +0200, Olaf Hering wrote:
>> > > > What is the recommended way to disable CONFIG_PV_SHIM, which is set in
>> > > > tools/firmware/Makefile? From my understanding there is no way to 
> influence
>> > > > its value from outside, which means the build always enters xen-dir/.
>> > > 
>> > > I think the following should do the trick.
>> > > 
>> > > Let me know if that works for you and I will submit it formally.
>> > > 
>> > > Thanks!
>> > > 
>> > > ---8<---
>> > > diff --git a/config/Tools.mk.in b/config/Tools.mk.in
>> > > index 98245f63c9..84ddb1a542 100644
>> > > --- a/config/Tools.mk.in
>> > > +++ b/config/Tools.mk.in
>> > > @@ -75,3 +75,5 @@ TINFO_LIBS          := @TINFO_LIBS@
>> > >  ARGP_LDFLAGS        := @argp_ldflags@
>> > >  
>> > >  FILE_OFFSET_BITS    := @FILE_OFFSET_BITS@
>> > > +
>> > > +CONFIG_PV_SHIM      := @pvshim@
>> > > diff --git a/tools/configure.ac b/tools/configure.ac
>> > > index c9fd69ddfa..8df2fd604b 100644
>> > > --- a/tools/configure.ac
>> > > +++ b/tools/configure.ac
>> > > @@ -492,4 +492,15 @@ AC_ARG_ENABLE([9pfs],
>> > >  
>> > >  AC_SUBST(ninepfs)
>> > >  
>> > > +AC_ARG_ENABLE([pvshim],
>> > > +    AS_HELP_STRING([--disable-pvshim], [Disable pvshim build (x86 only, 
>> > > enabled by default)]),
>> > > +    [AS_IF([test "x$enable_pvshim" = "xno"], [pvshim=n], [pvshim=y])], [
>> > > +    case "$host_cpu" in
>> > > +        i[[3456]]86|x86_64)
>> > > +           pvshim="y";;
>> > 
>> > Since xen doesn't build on 32bit anymore you may want to exclude
>> > i[3456]86 here?
>> 
>> Oh, I didn't realize this. Is it true for all distros?
> 
> FAOD I was thinking about 32bit xen support. But I just realise since
> you tested host_cpu here, maybe you intended to do a cross-build?

If the intention is a cross build, then host CPU shouldn't matter at
all, i.e. building e.g. on Arm should work as well.

When considering the target CPU, implying a 64-bit hypervisor from
a 32-bit general (i.e. tool stack) target would of course be an option.
Question just is how you would determine whether a suitable cross
tool chain is available.

> I have never tested cross-building 64bit xen on a 32bit platform...

As Andrew says - this works perfectly fine.

Jan


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