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powerpc/pseries: Limit machine check stack to 4GB

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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
This commit is contained in:
Nicholas Piggin 2020-05-08 14:34:01 +10:00 committed by Michael Ellerman
parent d7b14c5c04
commit d2cbbd45d4
1 changed files with 12 additions and 3 deletions
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15
arch/powerpc/kernel/setup_64.c
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@ -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
}
}