On Wed, Dec 14, 2016 at 10:51 PM, Paolo Bonzini <pbonz...@redhat.com> wrote: > >> I am looking at the possibility to add a new QEMU configuration option >> to make TCG optional (in qemu-system-*). What I am exploring is a way >> to exclude any of the TCG code not needed by KVM from the QEMU binary. >> There has been a previous attempt in the past from Paolo Bonzini, >> namely https://github.com/bonzini/qemu/tree/disable-tcg, that >> eventually was not upstreamed. I was looking into this work mainly, >> mostly to understand if the same approach can be respinned and used to >> support all the QEMU's targets. Any input on this is welcome. > > Yes, it sure can! However I suggest doing it one target at a time, > because there can be tricky dependencies between helper files and
Indeed, doing it gradually is the right way to tackle it. I might be back with some more concrete work. Thank you for the time being. > KVM support code. It's fine as long as the configure script only > allows --disable-tcg for specific targets where it works. > > IIRC my branch only covered x86 (or maybe PPC too?!? I don't remember). > > The hardest part is making sure that it doesn't bitrot, and it's hard > because we don't have CI for architectures other than x86. But at least > Peter builds on ARM, and target submaintainers do build on PPC and s390 > so it's not that bad perhaps. Would a CI set up just to test this feature make sense? Thank you, alvise > >> I was also wondering if an approach could be based on the recent patch >> series that allows to use the TCG frontend as a library -- >> https://www.mail-archive.com/qemu-devel@nongnu.org/msg415514.html. >> Making qemu-user and qemu-system users of such a library might help in >> having TCG optional. Obviously this solution introduces many other >> challenges and I'm not even sure if it's actually viable. > > I think making qemu-system use such a library would be very hard, because > of the different implementation of qemu_ld/qemu_st in user and system > emulation. I don't think it's important for your purpose. > > Paolo
