Commit 5c9fb189 authored Oct 15, 2014 by Greg Kurz Committed by Michael Ellerman Oct 16, 2014

powerpc/vphn: NUMA node code expects big-endian



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 b08a2a12
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>

parent 4a77f2bd

arch/powerpc/mm/numa.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1460,8 +1460,11 @@ 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;

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