Re: [Qemu-ppc] [PATCH RFC 0/4] Enable MTTCG on PowerPC

[Benjamin Herrenschmidt]

On Fri, 2016-09-02 at 12:02 +0530, Nikunj A Dadhania wrote:
> The series is a first attempt at enabling Multi-Threaded TCG on PowerPC.
> Changes that were needed to enable PowerPC are pretty simple;
> 
> Patch 01: Take a iothread lock during hcall, as hcall can generate io requests
>       02: For TCG, we were harcoding smt as 1, this gets rid of the limitation

If we do this, we need to implement the shared SPRs properly and the
inter-thread doorbells...

>       03: Use atomic_cmpxchg in store conditional
>       04: With more threads, flush the entry from each cpu. 
>         This can be optimized further.
> 
> The patches are based on the Alex Bennee's base enabling patches for 
> MTTCG[1] and Emilios's cmpxchg atomics. The consolidated tree of the 
> above patches is here:
> 
> https://github.com/stsquad/qemu/tree/mttcg/base-patches-v4-with-cmpxchg-atomics-v2
> 
> Apart from the above, PPC patches are based out of ppc-for-2.8 and 
> load/store consolidation patches [2]
> 
> Series with all dependent patches available here: 
> https://github.com/nikunjad/qemu/tree/ppc_mttcg_v1
> 
> Testing: 
> ========
> 
> -smp 4,cores=1,threads=4 -accel tcg,thread=multi
> 
> TODO
> ====
> Implement msgsndp instructions(door-bell), newer kernels enable it 
> depending on the PVR. I have been using following workaround to boot.
> https://github.com/nikunjad/qemu/commit/2c10052c5f93418a6b920e6ba3ce1813fcf50bc4
> 
> [1] https://www.mail-archive.com/address@hidden/msg391966.html
> [2] https://lists.gnu.org/archive/html/qemu-ppc/2016-08/msg00265.html
> 
> Nikunj A Dadhania (4):
>   spapr-hcall: take iothread lock during handler call
>   target-ppc: with MTTCG report more threads
>   target-ppc: use atomic_cmpxchg for ld/st reservation
>   target-ppc: flush tlb from all the cpu
> 
>  cputlb.c                | 15 +++++++++++++++
>  hw/ppc/spapr_hcall.c    | 11 +++++++++--
>  include/exec/exec-all.h |  2 ++
>  target-ppc/kvm.c        |  2 +-
>  target-ppc/kvm_ppc.h    |  2 +-
>  target-ppc/mmu-hash64.c |  2 +-
>  target-ppc/translate.c  | 24 +++++++++++++++++++++---
>  7 files changed, 50 insertions(+), 8 deletions(-)
>