Subject: Re: [PATCH] powerpc/powernv: Fix local TLB flush for boot and MCE on POWER9

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Fri, 07 Jul 2017 12:48:14 +0530

Nicholas Piggin <[email-masked]> writes:

> There are two cases outside the normal address space management
> where a CPU's local TLB is to be flushed:
>
>   1. Host boot; in case something has left stale entries in the
>      TLB (e.g., kexec).
>
>   2. Machine check; to clean corrupted TLB entries.
>
> CPU state restore from deep idle states also flushes the TLB.
> However this seems to be a side effect of reusing the boot code to set
> CPU state, rather than a requirement itself.
>
> The current flushing has a number of problems with ISA v3.0B:
>
> - The current radix mode of the MMU is not taken into account. tlbiel
>   is undefined if the R field does not match the current radix mode.
>
> - ISA v3.0B hash must flush the partition and process table caches.
>
> - ISA v3.0B radix must flush partition and process scoped translations,
>   partition and process table caches, and also the page walk cache.
>
> Add POWER9 cases to handle these, with radix vs hash determined by the
> host MMU mode.
>
> Signed-off-by: Nicholas Piggin <[email-masked]>

Reviewed-by: Aneesh Kumar K.V <[email-masked]>

> ---
>
> This is a relatively minimal version which does not churn code too
> much or remove flushing from the CPU deep state idle restore path.
> Should be suitable for stable after some upstream testing.
>
> Thanks,
> Nick
>
>  arch/powerpc/kernel/cpu_setup_power.S | 13 ++++++--
>  arch/powerpc/kernel/dt_cpu_ftrs.c     | 13 ++------
>  arch/powerpc/kernel/mce_power.c       | 56 ++++++++++++++++++++++++++++++++++-
>  3 files changed, 67 insertions(+), 15 deletions(-)
>
> diff --git a/arch/powerpc/kernel/cpu_setup_power.S b/arch/powerpc/kernel/cpu_setup_power.S
> index 10cb2896b2ae..610955fe8b81 100644
> --- a/arch/powerpc/kernel/cpu_setup_power.S
> +++ b/arch/powerpc/kernel/cpu_setup_power.S
> @@ -218,13 +218,20 @@ __init_tlb_power8:
>  	ptesync
>  1:	blr
>
> +/*
> + * Flush the TLB in hash mode. Hash must flush with RIC=2 once for process
> + * and one for partition scope to clear process and partition table entries.
> + */
>  __init_tlb_power9:
> -	li	r6,POWER9_TLB_SETS_HASH
> +	li	r6,POWER9_TLB_SETS_HASH - 1
>  	mtctr	r6
>  	li	r7,0xc00	/* IS field = 0b11 */
> +	li	r8,0
>  	ptesync
> -2:	tlbiel	r7
> -	addi	r7,r7,0x1000
> +	PPC_TLBIEL(7, 8, 2, 1, 0)
> +	PPC_TLBIEL(7, 8, 2, 0, 0)
> +2:	addi	r7,r7,0x1000
> +	PPC_TLBIEL(7, 8, 0, 0, 0)
>  	bdnz	2b
>  	ptesync
>  1:	blr
> diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
> index 4c7656dc4e04..b0da3718437d 100644
> --- a/arch/powerpc/kernel/dt_cpu_ftrs.c
> +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
> @@ -105,24 +105,15 @@ static void cpufeatures_flush_tlb(void)
>  	case PVR_POWER8:
>  	case PVR_POWER8E:
>  	case PVR_POWER8NVL:
> -		num_sets = POWER8_TLB_SETS;
> +		__flush_tlb_power8(POWER8_TLB_SETS);
>  		break;
>  	case PVR_POWER9:
> -		num_sets = POWER9_TLB_SETS_HASH;
> +		__flush_tlb_power9(POWER9_TLB_SETS_HASH);
>  		break;
>  	default:
> -		num_sets = 1;
>  		pr_err("unknown CPU version for boot TLB flush\n");
>  		break;
>  	}
> -
> -	asm volatile("ptesync" : : : "memory");
> -	rb = TLBIEL_INVAL_SET;
> -	for (i = 0; i < num_sets; i++) {
> -		asm volatile("tlbiel %0" : : "r" (rb));
> -		rb += 1 << TLBIEL_INVAL_SET_SHIFT;
> -	}
> -	asm volatile("ptesync" : : : "memory");
>  }
>
>  static void __restore_cpu_cpufeatures(void)
> diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
> index d24e689e893f..b76ca198e09c 100644
> --- a/arch/powerpc/kernel/mce_power.c
> +++ b/arch/powerpc/kernel/mce_power.c
> @@ -53,6 +53,60 @@ static void flush_tlb_206(unsigned int num_sets, unsigned int action)
>  	asm volatile("ptesync" : : : "memory");
>  }
>
> +static void flush_tlb_300(unsigned int num_sets, unsigned int action)
> +{
> +	unsigned long rb;
> +	unsigned int i;
> +	unsigned int r;
> +
> +	switch (action) {
> +	case TLB_INVAL_SCOPE_GLOBAL:
> +		rb = TLBIEL_INVAL_SET;
> +		break;
> +	case TLB_INVAL_SCOPE_LPID:
> +		rb = TLBIEL_INVAL_SET_LPID;
> +		break;
> +	default:
> +		BUG();
> +		break;
> +	}
> +
> +	asm volatile("ptesync" : : : "memory");
> +
> +	if (early_radix_enabled())
> +		r = 1;
> +	else
> +		r = 0;
> +
> +	/*
> +	 * First flush table/PWC caches with set 0, then flush the
> +	 * rest of the sets, partition scope. Radix must then do it
> +	 * all again with process scope. Hash just has to flush
> +	 * process table.
> +	 */
> +	asm volatile(PPC_TLBIEL(%0, %1, %2, %3, %4) : :
> +			"r"(rb), "r"(0), "i"(2), "i"(0), "r"(r));
> +	for (i = 1; i < num_sets; i++) {
> +		unsigned long set = i * (1<<TLBIEL_INVAL_SET_SHIFT);
> +
> +		asm volatile(PPC_TLBIEL(%0, %1, %2, %3, %4) : :
> +				"r"(rb+set), "r"(0), "i"(2), "i"(0), "r"(r));
> +	}
> +
> +	asm volatile(PPC_TLBIEL(%0, %1, %2, %3, %4) : :
> +			"r"(rb), "r"(0), "i"(2), "i"(1), "r"(r));
> +	if (early_radix_enabled()) {
> +		for (i = 1; i < num_sets; i++) {
> +			unsigned long set = i * (1<<TLBIEL_INVAL_SET_SHIFT);
> +
> +			asm volatile(PPC_TLBIEL(%0, %1, %2, %3, %4) : :
> +				"r"(rb+set), "r"(0), "i"(2), "i"(1), "r"(r));
> +		}
> +	}
> +
> +	asm volatile("ptesync" : : : "memory");
> +}
> +
>  /*
>   * Generic routines to flush TLB on POWER processors. These routines
>   * are used as flush_tlb hook in the cpu_spec.
> @@ -79,7 +133,7 @@ void __flush_tlb_power9(unsigned int action)
>  	else
>  		num_sets = POWER9_TLB_SETS_HASH;
>
> -	flush_tlb_206(num_sets, action);
> +	flush_tlb_300(num_sets, action);
>  }
>
>
> -- 
> 2.11.0