[PATCH v3 09/15] powerpc/pseries: limit machine check stack to 4GB
Nicholas Piggin
npiggin at gmail.com
Tue Apr 7 15:16:30 AEST 2020
This allows rtas_args to be put on the machine check stack, which
avoids a lot of complications with re-entrancy deadlocks.
Reviewed-by: Mahesh Salgaonkar <mahesh at linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
arch/powerpc/kernel/setup_64.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 438a9befce41..defe05b6b7a9 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -709,7 +709,7 @@ void __init exc_lvl_early_init(void)
*/
void __init emergency_stack_init(void)
{
- u64 limit;
+ u64 limit, mce_limit;
unsigned int i;
/*
@@ -726,7 +726,16 @@ void __init emergency_stack_init(void)
* initialized in kernel/irq.c. These are initialized here in order
* to have emergency stacks available as early as possible.
*/
- limit = min(ppc64_bolted_size(), ppc64_rma_size);
+ limit = mce_limit = min(ppc64_bolted_size(), ppc64_rma_size);
+
+ /*
+ * Machine check on pseries calls rtas, but can't use the static
+ * rtas_args due to a machine check hitting while the lock is held.
+ * rtas args have to be under 4GB, so the machine check stack is
+ * limited to 4GB so args can be put on stack.
+ */
+ if (firmware_has_feature(FW_FEATURE_LPAR) && mce_limit > SZ_4G)
+ mce_limit = SZ_4G;
for_each_possible_cpu(i) {
paca_ptrs[i]->emergency_sp = alloc_stack(limit, i) + THREAD_SIZE;
@@ -736,7 +745,7 @@ void __init emergency_stack_init(void)
paca_ptrs[i]->nmi_emergency_sp = alloc_stack(limit, i) + THREAD_SIZE;
/* emergency stack for machine check exception handling. */
- paca_ptrs[i]->mc_emergency_sp = alloc_stack(limit, i) + THREAD_SIZE;
+ paca_ptrs[i]->mc_emergency_sp = alloc_stack(mce_limit, i) + THREAD_SIZE;
#endif
}
}
--
2.23.0
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