[Trusty/Utopic,SRU] powerpc/vphn: NUMA node code expects big-endian

From: Greg Kurz <gkurz@linux.vnet.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1401150

The associativity domain numbers are obtained from the hypervisor through
registers and written into memory by the guest: the packed array passed to
vphn_unpack_associativity() is then native-endian, unlike what was assumed
in the following commit:

commit b08a2a12e44eaec5024b2b969f4fcb98169d1ca3
Author: Alistair Popple <alistair@popple.id.au>
Date:   Wed Aug 7 02:01:44 2013 +1000

    powerpc: Make NUMA device node code endian safe

This issue fills the topology with bogus data and makes it unusable. It may
lead to severe performance breakdowns.

We should ideally patch the vphn_unpack_associativity() function to do the
64-bit loads, but this requires some more brain storming.

In the meantime, let's go for a suboptimal and temporary bug fix: this patch
converts each 64-bit value of the packed array to big endian, as expected by
the current parsing code in vphn_unpack_associativity().

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit 5c9fb1899400096c6818181c525897a31d57e488)
Signed-off-by: Chris J Arges <chris.j.arges@canonical.com>
---
 arch/powerpc/mm/numa.c | 3 +++
 1 file changed, 3 insertions(+)

On Mon, Dec 15, 2014 at 11:11:55AM -0600, Chris J Arges wrote:
> From: Greg Kurz <gkurz@linux.vnet.ibm.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1401150
> 
> The associativity domain numbers are obtained from the hypervisor through
> registers and written into memory by the guest: the packed array passed to
> vphn_unpack_associativity() is then native-endian, unlike what was assumed
> in the following commit:
> 
> commit b08a2a12e44eaec5024b2b969f4fcb98169d1ca3 > Author: Alistair Popple <alistair@popple.id.au>
> Date:   Wed Aug 7 02:01:44 2013 +1000
> 
>     powerpc: Make NUMA device node code endian safe
> 
> This issue fills the topology with bogus data and makes it unusable. It may
> lead to severe performance breakdowns.
> 
> We should ideally patch the vphn_unpack_associativity() function to do the
> 64-bit loads, but this requires some more brain storming.
> 
> In the meantime, let's go for a suboptimal and temporary bug fix: this patch
> converts each 64-bit value of the packed array to big endian, as expected by
> the current parsing code in vphn_unpack_associativity().
> 
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> (cherry picked from commit 5c9fb1899400096c6818181c525897a31d57e488)
> Signed-off-by: Chris J Arges <chris.j.arges@canonical.com>
> ---
>  arch/powerpc/mm/numa.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index c752d50..a115c56 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -1417,8 +1417,11 @@ static long hcall_vphn(unsigned long cpu, __be32 *associativity)
>  	long retbuf[PLPAR_HCALL9_BUFSIZE] = {0};
>  	u64 flags = 1;
>  	int hwcpu = get_hard_smp_processor_id(cpu);
> +	int i;
>  
>  	rc = plpar_hcall9(H_HOME_NODE_ASSOCIATIVITY, retbuf, flags, hwcpu);
> +	for (i = 0; i < 6; i++)
> +		retbuf[i] = cpu_to_be64(retbuf[i]);
>  	vphn_unpack_associativity(retbuf, associativity);
>  
>  	return rc;

Uggg.  I assume that as this is "temporary" that someone will make this
6 go away upstream.  Nasty.

Acked-by: Andy Whitcroft <apw@canonical.com>

-apw

Applied to Trusty and Utopic.

-apw