Re: [Qemu-ppc] [QEMU-PPC] [PATCH 2/3] target/ppc: Don't require private l1d cache on POWER8 for cap_ppc_safe_cache

[David Gibson]

On Fri, May 11, 2018 at 04:25:08PM +1000, Suraj Jitindar Singh wrote:
> For cap_ppc_safe_cache to be set to workaround, we require both a l1d
> cache flush instruction and private l1d cache.
> 
> On POWER8 don't require private l1d cache. This means a guest on a
> POWER8 machine can make use of the cache flush workarounds.
> 
> Signed-off-by: Suraj Jitindar Singh <address@hidden>
> ---
>  target/ppc/kvm.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 2c0c34e125..7b33119b1a 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -2414,9 +2414,17 @@ bool kvmppc_has_cap_mmu_hash_v3(void)
>  
>  static int parse_cap_ppc_safe_cache(struct kvm_ppc_cpu_char c)
>  {
> +    PowerPCCPUClass *pcc = kvm_ppc_get_host_cpu_class();
> +    bool l1d_thread_priv_req = true;
> +
> +    if (pcc->pvr_match(pcc, CPU_POWERPC_POWER8_BASE)) {
> +        l1d_thread_priv_req = false;
> +    }

So, I think the thread discussing this test got a bit sidetracked.
Going via the host cpu class and pvr_match objects seems a convoluted
way of going about this though.  I think it would be clearer to just
directly call mfpvr() and mask/test it.

> +
>      if (~c.behaviour & c.behaviour_mask & H_CPU_BEHAV_L1D_FLUSH_PR) {
>          return 2;
> -    } else if ((c.character & c.character_mask & H_CPU_CHAR_L1D_THREAD_PRIV) 
> &&
> +    } else if ((!l1d_thread_priv_req ||
> +                c.character & c.character_mask & H_CPU_CHAR_L1D_THREAD_PRIV) 
> &&
>                 (c.character & c.character_mask
>                  & (H_CPU_CHAR_L1D_FLUSH_ORI30 | 
> H_CPU_CHAR_L1D_FLUSH_TRIG2))) {
>          return 1;

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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