ARCv2: mm: THP support
MMUv4 in HS38x cores supports Super Pages which are basis for Linux THP
support.
Normal and Super pages can co-exist (ofcourse not overlap) in TLB with a
new bit "SZ" in TLB page desciptor to distinguish between them.
Super Page size is configurable in hardware (4K to 16M), but fixed once
RTL builds.
The exact THP size a Linx configuration will support is a function of:
- MMU page size (typical 8K, RTL fixed)
- software page walker address split between PGD:PTE:PFN (typical
11:8:13, but can be changed with 1 line)
So for above default, THP size supported is 8K * 256 = 2M
Default Page Walker is 2 levels, PGD:PTE:PFN, which in THP regime
reduces to 1 level (as PTE is folded into PGD and canonically referred
to as PMD).
Thus thp PMD accessors are implemented in terms of PTE (just like sparc)
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/mm/tlbex.S b/arch/arc/mm/tlbex.S
index b8b014c..5525948 100644
--- a/arch/arc/mm/tlbex.S
+++ b/arch/arc/mm/tlbex.S
@@ -205,10 +205,18 @@
#endif
lsr r0, r2, PGDIR_SHIFT ; Bits for indexing into PGD
- ld.as r1, [r1, r0] ; PGD entry corresp to faulting addr
- and.f r1, r1, PAGE_MASK ; Ignoring protection and other flags
- ; contains Ptr to Page Table
- bz.d do_slow_path_pf ; if no Page Table, do page fault
+ ld.as r3, [r1, r0] ; PGD entry corresp to faulting addr
+ tst r3, r3
+ bz do_slow_path_pf ; if no Page Table, do page fault
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ and.f 0, r3, _PAGE_HW_SZ ; Is this Huge PMD (thp)
+ add2.nz r1, r1, r0
+ bnz.d 2f ; YES: PGD == PMD has THP PTE: stop pgd walk
+ mov.nz r0, r3
+
+#endif
+ and r1, r3, PAGE_MASK
; Get the PTE entry: The idea is
; (1) x = addr >> PAGE_SHIFT -> masks page-off bits from @fault-addr
@@ -219,6 +227,9 @@
lsr r0, r2, (PAGE_SHIFT - 2)
and r0, r0, ( (PTRS_PER_PTE - 1) << 2)
ld.aw r0, [r1, r0] ; get PTE and PTE ptr for fault addr
+
+2:
+
#ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT
and.f 0, r0, _PAGE_PRESENT
bz 1f