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powerpc/powernv: Fix oops on P9 DD1 in cause_ipi()

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Recently we merged the native xive support for Power9, and then separately some
reworks for doorbell IPI support. In isolation both series were OK, but the
merged result had a bug in one case.

On P9 DD1 we use pnv_p9_dd1_cause_ipi() which tries to use doorbells, and then
falls back to the interrupt controller. However the fallback is implemented by
calling icp_ops->cause_ipi. But now that xive support is merged we might be
using xive, in which case icp_ops is not initialised, it's a xics specific
structure. This leads to an oops such as:

  Unable to handle kernel paging request for data at address 0x00000028
  Oops: Kernel access of bad area, sig: 11 [#1]
  NIP pnv_p9_dd1_cause_ipi+0x74/0xe0
  LR smp_muxed_ipi_message_pass+0x54/0x70

To fix it, rather than using icp_ops which might be NULL, have both xics and
xive set smp_ops->cause_ipi, and then in the powernv code we save that as
ic_cause_ipi before overriding smp_ops->cause_ipi. For paranoia add a WARN_ON()
to check if somehow smp_ops->cause_ipi is NULL.

Fixes: b866cc2199 ("powerpc: Change the doorbell IPI calling convention")
Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Michael Ellerman 2017-04-26 17:32:38 +10:00
parent 83c4919058
commit 45b21cfeb2
2 changed files with 11 additions and 4 deletions
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12
arch/powerpc/platforms/powernv/smp.c
View file

@ -249,12 +249,15 @@ static int pnv_smp_prepare_cpu(int cpu)
return 0;
}
/* Cause IPI as setup by the interrupt controller (xics or xive) */
static void (*ic_cause_ipi)(int cpu);
static void pnv_cause_ipi(int cpu)
{
if (doorbell_try_core_ipi(cpu))
return;
icp_ops->cause_ipi(cpu);
ic_cause_ipi(cpu);
}
static void pnv_p9_dd1_cause_ipi(int cpu)
@ -269,7 +272,7 @@ static void pnv_p9_dd1_cause_ipi(int cpu)
if (cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu)))
doorbell_global_ipi(cpu);
else
icp_ops->cause_ipi(cpu);
ic_cause_ipi(cpu);
put_cpu();
}
@ -282,6 +285,9 @@ static void __init pnv_smp_probe(void)
xics_smp_probe();
if (cpu_has_feature(CPU_FTR_DBELL)) {
ic_cause_ipi = smp_ops->cause_ipi;
WARN_ON(!ic_cause_ipi);
if (cpu_has_feature(CPU_FTR_ARCH_300)) {
if (cpu_has_feature(CPU_FTR_POWER9_DD1))
smp_ops->cause_ipi = pnv_p9_dd1_cause_ipi;
@ -290,8 +296,6 @@ static void __init pnv_smp_probe(void)
} else {
smp_ops->cause_ipi = pnv_cause_ipi;
}
} else {
smp_ops->cause_ipi = icp_ops->cause_ipi;
}
}

3
arch/powerpc/sysdev/xics/xics-common.c
View file

@ -145,6 +145,9 @@ void __init xics_smp_probe(void)
{
/* Register all the IPIs */
xics_request_ipi();
/* Setup cause_ipi callback based on which ICP is used */
smp_ops->cause_ipi = icp_ops->cause_ipi;
}
#endif /* CONFIG_SMP */