Re: [PATCH 2/2] KVM: PPC: Book3S HV: lockless tlbie for HPT hcalls

[Michael Ellerman]

Nicholas Piggin <npig...@gmail.com> writes:
> diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c 
> b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> index 78e6a392330f..0221a0f74f07 100644
> --- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> +++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
> @@ -439,6 +439,9 @@ static inline int try_lock_tlbie(unsigned int *lock)
>       unsigned int tmp, old;
>       unsigned int token = LOCK_TOKEN;
>  
> +     if (mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE))
> +             return 1;
> +
>       asm volatile("1:lwarx   %1,0,%2\n"
>                    "  cmpwi   cr0,%1,0\n"
>                    "  bne     2f\n"
> @@ -452,6 +455,12 @@ static inline int try_lock_tlbie(unsigned int *lock)
>       return old == 0;
>  }
>  
> +static inline void unlock_tlbie_after_sync(unsigned int *lock)
> +{
> +     if (mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE))
> +             return;
> +}

So this is a bit hard to follow:

#define MMU_FTRS_DEFAULT_HPTE_ARCH_V2   \
        MMU_FTR_HPTE_TABLE | MMU_FTR_PPCAS_ARCH_V2
#define MMU_FTRS_POWER          MMU_FTRS_DEFAULT_HPTE_ARCH_V2
#define MMU_FTRS_PPC970         MMU_FTRS_POWER | MMU_FTR_TLBIE_CROP_VA          
        // does NOT
#define MMU_FTRS_POWER5         MMU_FTRS_POWER | MMU_FTR_LOCKLESS_TLBIE
#define MMU_FTRS_POWER6         MMU_FTRS_POWER5 | MMU_FTR_KERNEL_RO | 
MMU_FTR_68_BIT_VA // includes lockless TLBIE
#define MMU_FTRS_POWER7         MMU_FTRS_POWER6                                 
        // includes lockless TLBIE
#define MMU_FTRS_POWER8         MMU_FTRS_POWER6                                 
        // includes lockless TLBIE
#define MMU_FTRS_POWER9         MMU_FTRS_POWER6                                 
        // includes lockless TLBIE
#define MMU_FTRS_CELL           MMU_FTRS_DEFAULT_HPTE_ARCH_V2 |                 
        // does NOT
                                MMU_FTR_CI_LARGE_PAGE
#define MMU_FTRS_PA6T           MMU_FTRS_DEFAULT_HPTE_ARCH_V2 | \               
        // does NOT
                                MMU_FTR_CI_LARGE_PAGE | MMU_FTR_NO_SLBIE_B


So it's only 970, Cell and Pasemi that *don't* have lockless TLBIE.

And KVM HV doesn't doesn't run on any of those.

So we can just not check for the feature in the KVM HV code.

Am I right?

cheers