The logic used to split the r4000 refill handler is liberally
sprinkled with magic numbers. We attempt to explain what they are and
normalize them against a new symbolic value (MIPS64_REFILL_INSNS).
Changes from v1: Corrected spelling in comment.
CC: David VomLehn <dvomlehn@xxxxxxxxx>
Reviewed-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Signed-off-by: David Daney <ddaney@xxxxxxxxxxxxxxxxxx>
---
arch/mips/mm/tlbex.c | 34 ++++++++++++++++++++++++++--------
1 files changed, 26 insertions(+), 8 deletions(-)
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 4dc4f3e..cbc09de 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -649,6 +649,14 @@ static void __cpuinit build_update_entries(u32 **p, unsigned int tmp,
#endif
}
+/*
+ * For a 64-bit kernel, we are using the 64-bit XTLB refill exception
+ * because EXL == 0. If we wrap, we can also use the 32 instruction
+ * slots before the XTLB refill exception handler which belong to the
+ * unused TLB refill exception.
+ */
+#define MIPS64_REFILL_INSNS 32
+
static void __cpuinit build_r4000_tlb_refill_handler(void)
{
u32 *p = tlb_handler;
@@ -702,9 +710,10 @@ static void __cpuinit build_r4000_tlb_refill_handler(void)
if ((p - tlb_handler) > 64)
panic("TLB refill handler space exceeded");
#else
- if (((p - tlb_handler) > 63)
- || (((p - tlb_handler) > 61)
- && uasm_insn_has_bdelay(relocs, tlb_handler + 29)))
+ if (((p - tlb_handler) > (MIPS64_REFILL_INSNS * 2) - 1)
+ || (((p - tlb_handler) > (MIPS64_REFILL_INSNS * 2) - 3)
+ && uasm_insn_has_bdelay(relocs,
+ tlb_handler + MIPS64_REFILL_INSNS - 3)))
panic("TLB refill handler space exceeded");
#endif
@@ -717,16 +726,24 @@ static void __cpuinit build_r4000_tlb_refill_handler(void)
uasm_copy_handler(relocs, labels, tlb_handler, p, f);
final_len = p - tlb_handler;
#else /* CONFIG_64BIT */
- f = final_handler + 32;
- if ((p - tlb_handler) <= 32) {
+ f = final_handler + MIPS64_REFILL_INSNS;
+ if ((p - tlb_handler) <= MIPS64_REFILL_INSNS) {
/* Just copy the handler. */
uasm_copy_handler(relocs, labels, tlb_handler, p, f);
final_len = p - tlb_handler;
} else {
- u32 *split = tlb_handler + 30;
+ /*
+ * Split two instructions before the end. One for the
+ * branch and one for the instruction in the delay
+ * slot.
+ */
+ u32 *split = tlb_handler + MIPS64_REFILL_INSNS - 2;
/*
- * Find the split point.
+ * Find the split point. If the branch would fall in
+ * a delay slot, we must back up an additional
+ * instruction so that it is no longer in a delay
+ * slot.
*/
if (uasm_insn_has_bdelay(relocs, split - 1))
split--;
@@ -749,7 +766,8 @@ static void __cpuinit build_r4000_tlb_refill_handler(void)
/* Copy the rest of the handler. */
uasm_copy_handler(relocs, labels, split, p, final_handler);
- final_len = (f - (final_handler + 32)) + (p - split);
+ final_len = (f - (final_handler + MIPS64_REFILL_INSNS)) +
+ (p - split);
}
#endif /* CONFIG_64BIT */
--
1.6.0.6
