From 45b21cfeb22087795f0b49397fbe529efeb99baf Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 26 Apr 2017 17:32:38 +1000 Subject: [PATCH] powerpc/powernv: Fix oops on P9 DD1 in cause_ipi() 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: b866cc2199d6 ("powerpc: Change the doorbell IPI calling convention") Tested-by: Gautham R. Shenoy Signed-off-by: Michael Ellerman --- arch/powerpc/platforms/powernv/smp.c | 12 ++++++++---- arch/powerpc/sysdev/xics/xics-common.c | 3 +++ 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c index 951a2e2..5189445 100644 --- a/arch/powerpc/platforms/powernv/smp.c +++ b/arch/powerpc/platforms/powernv/smp.c @@ -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; } } diff --git a/arch/powerpc/sysdev/xics/xics-common.c b/arch/powerpc/sysdev/xics/xics-common.c index 2eb53c1..ffe138b 100644 --- a/arch/powerpc/sysdev/xics/xics-common.c +++ b/arch/powerpc/sysdev/xics/xics-common.c @@ -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 */ -- 2.7.4