powerpc/64s: Relax PACA address limitations

Book3S PACA memory allocation is restricted by the RMA limit and also
must not take SLB faults when accessed in virtual mode. Currently a
fixed 256MB limit is used for this, which is imprecise and sub-optimal.

Update the paca allocation limits to use use the ppc64_rma_size for RMA
limit, and share the safe_stack_limit() that is currently used for stack
allocations that must not take virtual mode faults.

The safe_stack_limit() name is changed to ppc64_bolted_size() to match
ppc64_rma_size and some comments are updated. We also need to use
early_mmu_has_feature() because we are now calling this function prior
to the jump label patching that enables mmu_has_feature().

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Change mmu_has_feature() to early_mmu_has_feature()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 7 insertions, 6 deletions

diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index d6597038931d..95ffedf14885 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -18,6 +18,8 @@
 #include <asm/pgtable.h>
 #include <asm/kexec.h>
 
+#include "setup.h"
+
 #ifdef CONFIG_PPC_BOOK3S
 
 /*
@@ -208,15 +210,14 @@ void __init allocate_pacas(void)
 	u64 limit;
 	int cpu;
 
-	limit = ppc64_rma_size;
-
 #ifdef CONFIG_PPC_BOOK3S_64
 	/*
-	 * We can't take SLB misses on the paca, and we want to access them
-	 * in real mode, so allocate them within the RMA and also within
-	 * the first segment.
+	 * We access pacas in real mode, and cannot take SLB faults
+	 * on them when in virtual mode, so allocate them accordingly.
 	 */
-	limit = min(0x10000000ULL, limit);
+	limit = min(ppc64_bolted_size(), ppc64_rma_size);
+#else
+	limit = ppc64_rma_size;
 #endif
 
 	paca_size = PAGE_ALIGN(sizeof(struct paca_struct) * nr_cpu_ids);