Re: [Xen-devel] Build problems with xen 4.7

[George Dunlap <dunlapg@xxxxxxxxx>]

On Tue, Jun 7, 2016 at 12:33 PM, Doug Goldstein <cardoe@xxxxxxxxxx> wrote:
> On 6/7/16 6:42 AM, M A Young wrote:
>> On Tue, 7 Jun 2016, George Dunlap wrote:
>>
>>> On Fri, May 13, 2016 at 4:23 PM, Konrad Rzeszutek Wilk
>>> <konrad.wilk@xxxxxxxxxx> wrote:
>>>> --- xen-4.7.0/config/StdGNU.mk.orig     2016-04-15 22:56:52.191227591 +0100
>>>> +++ xen-4.7.0/config/StdGNU.mk  2016-04-15 23:01:40.978829756 +0100
>>>> @@ -37,6 +37,12 @@
>>>>
>>>>  ifneq ($(debug),y)
>>>>  CFLAGS += -O2 -fomit-frame-pointer -fno-tree-coalesce-vars
>>>> +ifeq ($(XEN_TARGET_ARCH),x86_64)
>>>> +#might be cross-compiling so strip out possible x86_32 options
>>>> +CFLAGS += $(shell echo $(CFLAGS_EXTRA) | sed -e 's/-m32//g' -e 
>>>> 's/-march=i686//g' -e 's/-mtune=atom//g')
>>>> +else
>>>> +CFLAGS += $(CFLAGS_EXTRA)
>>>> +endif
>>>
>>> Why the if?  Under what circumstances is it actually appropriate to
>>> pass in those kinds of flags to the Xen build system?
>>
>> That may not be needed in general. It is something I added for Fedora as I
>> am cross-compiling the hypervisor as x86_64 to put in the i686 package
>> because ix86 hypervisors are no longer supported.
>>
>>       Michael Young
>>
>
> I have to say looking at the change and looking at the reason there
> appears to be something very wrong with this. If you cross compile you
> shouldn't have to strip out your BUILD_ARCH's CFLAGS from your
> TARGET_ARCH's CFLAGS. It seems like somewhere those are getting crossed
> together and that needs to be fixed rather than patching Xen.

But I think these are *in general* meant to be the TARGET_ARCH's
cflags.  Michael is building packages for 32-bit fedora, so the tools
and everything actually do want to be 32-bit.  It's just the
hypervisor which is special -- it has to be compiled 64-bit even when
building "32-bit" packages.  So the -m32 needs to be filtered out of
the TARGET_ARCH -- the question is whether it should be done in the
makefiles, or in the RPM spec file.  I'm inclined to say the latter.

 -George

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