linux-kernel - Re: [PATCH] powerpc/powernv: Initialise nest mmu

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Message-ID: <20160815072240.GA21080@balbir.ozlabs.ibm.com>
Date:	Mon, 15 Aug 2016 17:22:40 +1000
From:	Balbir Singh <bsingharora@...il.com>
To:	Alistair Popple <alistair@...ple.id.au>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	benh@...nel.crashing.org, stewart@...ux.vnet.ibm.com,
	bsingharora@...il.com, mpe@...erman.id.au
Subject: Re: [PATCH] powerpc/powernv: Initialise nest mmu

On Mon, Aug 15, 2016 at 04:51:59PM +1000, Alistair Popple wrote:
> POWER9 contains an off core mmu called the nest mmu (NMMU). This is
> used by other hardware units on the chip to translate virtual
> addresses into real addresses. The unit attempting an address
> translation provides the majority of the context required for the
> translation request except for the base address of the partition table
> (ie. the PTCR) which needs to be programmed into the NMMU.
> 
> This patch adds a call to OPAL to set the PTCR for the nest mmu in
> opal_init().
> 
> Signed-off-by: Alistair Popple <alistair@...ple.id.au>
> ---
> 
> This patch depends on a new OPAL call which has yet to be added to
> skiboot, although the patch to do so has been posted to
> http://patchwork.ozlabs.org/patch/659106/
> 
>  arch/powerpc/include/asm/opal-api.h            | 3 ++-
>  arch/powerpc/include/asm/opal.h                | 1 +
>  arch/powerpc/platforms/powernv/opal-wrappers.S | 1 +
>  arch/powerpc/platforms/powernv/opal.c          | 3 +++
>  4 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
> index 0e2e57b..a0aa285 100644
> --- a/arch/powerpc/include/asm/opal-api.h
> +++ b/arch/powerpc/include/asm/opal-api.h
> @@ -167,7 +167,8 @@
>  #define OPAL_INT_EOI				124
>  #define OPAL_INT_SET_MFRR			125
>  #define OPAL_PCI_TCE_KILL			126
> -#define OPAL_LAST				126
> +#define OPAL_NMMU_SET_PTCR			127
> +#define OPAL_LAST				127
> 
>  /* Device tree flags */
> 
> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index ee05bd2..433df5e 100644
> --- a/arch/powerpc/include/asm/opal.h
> +++ b/arch/powerpc/include/asm/opal.h
> @@ -228,6 +228,7 @@ int64_t opal_pci_tce_kill(uint64_t phb_id, uint32_t kill_type,
>  int64_t opal_rm_pci_tce_kill(uint64_t phb_id, uint32_t kill_type,
>  			     uint32_t pe_num, uint32_t tce_size,
>  			     uint64_t dma_addr, uint32_t npages);
> +int64_t opal_nmmu_set_ptcr(uint64_t chip_id, uint64_t ptcr);
> 
>  /* Internal functions */
>  extern int early_init_dt_scan_opal(unsigned long node, const char *uname,
> diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
> index 3d29d40..a955649 100644
> --- a/arch/powerpc/platforms/powernv/opal-wrappers.S
> +++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
> @@ -308,3 +308,4 @@ OPAL_CALL(opal_int_eoi,				OPAL_INT_EOI);
>  OPAL_CALL(opal_int_set_mfrr,			OPAL_INT_SET_MFRR);
>  OPAL_CALL(opal_pci_tce_kill,			OPAL_PCI_TCE_KILL);
>  OPAL_CALL_REAL(opal_rm_pci_tce_kill,		OPAL_PCI_TCE_KILL);
> +OPAL_CALL(opal_nmmu_set_ptcr,			OPAL_NMMU_SET_PTCR);
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index 8b4fc68..b533245 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -762,6 +762,9 @@ static int __init opal_init(void)
>  	/* Initialise OPAL kmsg dumper for flushing console on panic */
>  	opal_kmsg_init();
> 
> +	/* Update partition table control register on all Nest MMUs */
> +	opal_nmmu_set_ptcr(-1UL, __pa(partition_tb) | (PATB_SIZE_SHIFT - 12));
> +

Just wondering if

1. Instead of using -1 for all cpus, we should do
	for_each_online_cpu() {
		opal_numm_set_ptcr(...)
	}

2. In cpu hotplug path do the same when onlining and set to NULL on
offlining?

I think we should definitely try and become hotplug aware from the OS
view point and drive it from the OS

What do you think?

Balbir Singh.