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powerpc/pseries: Limit machine check stack to 4GB
This allows rtas_args to be put on the machine check stack, which avoids a lot of complications with re-entrancy deadlocks. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr> Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com> Link: https://lore.kernel.org/r/20200508043408.886394-10-npiggin@gmail.com
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1 changed files with 12 additions and 3 deletions
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@ -709,7 +709,7 @@ void __init exc_lvl_early_init(void)
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*/
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void __init emergency_stack_init(void)
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{
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u64 limit;
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u64 limit, mce_limit;
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unsigned int i;
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/*
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@ -726,7 +726,16 @@ void __init emergency_stack_init(void)
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* initialized in kernel/irq.c. These are initialized here in order
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* to have emergency stacks available as early as possible.
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*/
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limit = min(ppc64_bolted_size(), ppc64_rma_size);
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limit = mce_limit = min(ppc64_bolted_size(), ppc64_rma_size);
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/*
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* Machine check on pseries calls rtas, but can't use the static
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* rtas_args due to a machine check hitting while the lock is held.
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* rtas args have to be under 4GB, so the machine check stack is
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* limited to 4GB so args can be put on stack.
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*/
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if (firmware_has_feature(FW_FEATURE_LPAR) && mce_limit > SZ_4G)
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mce_limit = SZ_4G;
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for_each_possible_cpu(i) {
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paca_ptrs[i]->emergency_sp = alloc_stack(limit, i) + THREAD_SIZE;
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@ -736,7 +745,7 @@ void __init emergency_stack_init(void)
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paca_ptrs[i]->nmi_emergency_sp = alloc_stack(limit, i) + THREAD_SIZE;
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/* emergency stack for machine check exception handling. */
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paca_ptrs[i]->mc_emergency_sp = alloc_stack(limit, i) + THREAD_SIZE;
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paca_ptrs[i]->mc_emergency_sp = alloc_stack(mce_limit, i) + THREAD_SIZE;
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#endif
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}
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}
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