On 14/12/2016 20:30, Alvise Rigo wrote: > Hi all, > > 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. > > 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.
To have a library has also another interest: testing. For the moment RISU is doing a great job but it needs to be able to start a client (the apprentice) in a chroot. So it requires a "viable" TCG implementation. If we would have a library we could directly link the "apprentice" with the library and it will inject the code to test directly (without chroot) in the TCG engine. Moreover, I think we could use single-step instead of trap to synchronize master and apprentice. We had something like that to test 680x0 [1], but the main program was written in C++ compiling some parts of QEMU inside, and I failed to recompile it last time I tried (I use RISU now). Thanks, Laurent [1] https://github.com/vivier/m68k-tester
