From: Michael Ellerman <mpe@ellerman.id.au>
To: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: linuxppc-dev@ozlabs.org, mikey@neuling.org, nacc@linux.vnet.ibm.com
Subject: Re: [RFC] powerpc/numa: Use VPHN based node ID information on shared processor LPARs
Date: Fri, 16 Oct 2015 13:27:01 +1100 [thread overview]
Message-ID: <1444962421.28419.3.camel@ellerman.id.au> (raw)
In-Reply-To: <1444813335-4009-1-git-send-email-khandual@linux.vnet.ibm.com>
On Wed, 2015-10-14 at 14:32 +0530, Anshuman Khandual wrote:
> On shared processor LPARs, H_HOME_NODE_ASSOCIATIVITY hcall provides the
> dynamic virtual-physical mapping for any given processor. Currently we
> use VPHN node ID information only after getting either a PRRN or a VPHN
> event. But during boot time inside the function numa_setup_cpu, we still
> query the OF device tree for the node ID value which might be different
> than what can be fetched from the H_HOME_NODE_ASSOCIATIVITY hcall. In a
> scenario where there are no PRRN or VPHN event after boot, all node-cpu
> mapping will remain incorrect there after.
>
> With this proposed change, numa_setup_cpu will try to override the OF
> device tree fetched node ID information with H_HOME_NODE_ASSOCIATIVITY
> hcall fetched node ID value. Right now shared processor property of the
> LPAR cannot be queried as VPA inializaion happens after numa_setup_cpu
> during boot time. So initmem_init function has been moved after ppc_md.
> setup_arch inside setup_arch during boot.
>
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index 8b9502a..e404d05 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -553,6 +557,17 @@ static int numa_setup_cpu(unsigned long lcpu)
>
> nid = of_node_to_nid_single(cpu);
>
> + /*
> + * Override the OF device tree fetched node number
> + * with VPHN based node number in case of a shared
> + * processor LPAR on PHYP platform.
> + */
> +#ifdef CONFIG_PPC_SPLPAR
> + if (lppaca_shared_proc(get_lppaca())) {
> + nid = vphn_get_node(lcpu);
> + }
> +#endif
That logic exposes a potential problem which you don't seem to have addressed.
You're not updating the logic in of_node_to_nid[_single](), instead you're
overriding it in *this one location*. But what about other code that uses
of_node_to_nid()? It will still get the old device-tree value and so will have
the wrong nid, won't it?
cheers
next prev parent reply other threads:[~2015-10-16 2:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-14 9:02 [RFC] powerpc/numa: Use VPHN based node ID information on shared processor LPARs Anshuman Khandual
2015-10-14 9:19 ` Michael Ellerman
2015-10-14 10:13 ` Anshuman Khandual
2015-10-16 2:24 ` Michael Ellerman
2015-10-16 5:55 ` Anshuman Khandual
2015-10-16 2:27 ` Michael Ellerman [this message]
2015-10-16 5:55 ` Anshuman Khandual
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