[PATCH v4 09/16] powerpc/pseries: limit machine check stack to 4GB
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2020-05-08 04:55:33
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
This allows rtas_args to be put on the machine check stack, which avoids a lot of complications with re-entrancy deadlocks. Reviewed-by: Christophe Leroy <redacted> Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com> Signed-off-by: Nicholas Piggin <npiggin@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 8105010b0e76..bb47555d48a2 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c@@ -711,7 +711,7 @@ void __init exc_lvl_early_init(void) */ void __init emergency_stack_init(void) { - u64 limit; + u64 limit, mce_limit; unsigned int i; /*
@@ -728,7 +728,16 @@ 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;
@@ -738,7 +747,7 @@ 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 } }
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2.23.0