The kernel PUD refill path merges virtual address bits 32:28 into a
TTE, requiring hardware pages of at least 256MB. Sun4u instead selects
4MB pages, losing bits 27:22 when refilling a huge PUD. Sun4v also falls
back to 4MB pages when neither 256MB nor 2GB pages are selected.
Keep PMD mappings when the selected PUD encoding matches the small-page
entry. The PMD refill path preserves the bits needed by the 4MB TTE;
sun4v selections of 256MB or larger remain eligible for huge PUDs.
Fixes: 0dd5b7b09e13 ("sparc64: Fix physical memory management regressions with
large max_phys_bits.")
Cc: [email protected]
Signed-off-by: Magnus Lindholm <[email protected]>
---
arch/sparc/mm/init_64.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 103db4683b16..f3f7eba08469 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -1696,6 +1696,14 @@ static unsigned long __ref kernel_map_hugepud(unsigned
long vstart,
static bool kernel_can_map_hugepud(unsigned long vstart, unsigned long vend,
bool guard)
{
+ /*
+ * The PUD miss path propagates VA bits 32:28, assuming at least
+ * 256MB hardware pages. Retain PMD mappings when the selected PUD
+ * encoding falls back to the small-page entry.
+ */
+ if (kern_linear_pte_xor[2] == kern_linear_pte_xor[0])
+ return false;
+
if (guard && !(vstart & ~PUD_MASK) && (vend - vstart) >= PUD_SIZE)
return true;
--
2.43.0
