On 18.10.2021 12:40, Juergen Gross wrote: > On 18.10.21 12:36, Jan Beulich wrote: >> On 18.10.2021 12:28, Juergen Gross wrote: >>> On 18.10.21 11:51, Anthony PERARD wrote: >>>> On Mon, Oct 18, 2021 at 11:02:20AM +0200, Jan Beulich wrote: >>>>> On 15.10.2021 18:58, Anthony PERARD wrote: >>>>>> I have to think about that. I've made some further progress in order to >>>>>> be able to build the Xen pvhshim without a link farm and notice that >>>>>> nearly every source file needs to use "$(srctree)/$(src)" >>>>> >>>>> Oh, now I'm curious as to the why here. I thought use of $(srctree) >>>>> ought to be the exception. >>>> >>>> In Linux, the use of $(srctree) is indeed the exception. This is because >>>> we have VPATH=$(srctree), so when `make` look for a prerequisite or a >>>> target it will look first in the current directory and then in >>>> $(srctree). That works fine as long as the source tree only have sources >>>> and no built files. >>>> >>>> But if we want to be able to build the pv-shim without the linkfarm and >>>> thus using out-of-tree build, we are going to need the ability to build >>>> from a non-clean source tree. I don't think another way is possible. >>> >>> Is there any reason (apart from historical ones) to build the hypervisor >>> in $(srctree)? >>> >>> I could see several advantages to build it in another directory as soon >>> as the build system has this capability: >>> >>> - possibility to have a simple build target for building multiple archs >>> (assuming the cross-tools are available), leading to probably less >>> problems with breaking the build of "the other" architecture we are >>> normally not working with (and in future with e.g. Risc-V being added >>> this will be even more important) >>> >>> - possibility to have a debug and a non-debug build in parallel (in fact >>> at least at SUSE we are working around that by building those with an >>> intermediate "make clean" for being able to package both variants) >>> >>> - make clean for the hypervisor part would be just a "rm -r" >> >> I fully agree, yet ... >> >>> Yes, this would require us (the developers) to maybe change some habits, >>> but I think this would be better than working around the issues by >>> adding $(srctree) all over the build system. >> >> ... developers' habits would only be my second concern here (and if that >> had been the only one, then I would not see this as a reason speaking >> against the change, but as said I've never been building from the root, >> and I've also been building sort of out-of-tree all the time). Yet while >> writing this reply I came to realize that my primary concern was wrong: >> People would not need to adjust their spec files (or alike), at least >> not as long as they consume only files living under dist/. >> >> So, Anthony - thoughts about making the default in-tree Xen build >> actually build into, say, build/xen/? > > Or maybe even build-<arch>[-debug]/xen/?
I'd be okay with build-<arch>, but things would become questionable imo when considering further elements recorded in .config: Where would you draw the line? Jan
