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

[Cédric Le Goater]

On 09/02/2016 08:32 AM, 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
>       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

You could also introduce a Power8 DD1 in qemu. From the kernel cputable :

        {       /* Power8 DD1: Does not support doorbell IPIs */
                .pvr_mask               = 0xffffff00,
                .pvr_value              = 0x004d0100,
                .cpu_name               = "POWER8 (raw)",
                .cpu_features           = CPU_FTRS_POWER8_DD1,
                ...

Cheers,
C.