[Skiboot] [PATCH] xive: Fix VP free block group mode false-positive parameter check

[Nicholas Piggin]

The check to ensure the buddy allocation idx is aligned to its
allocation order was not taking into account the allocation split.
This would result in opal_xive_free_vp_block failures despite
giving the same value as returned by opal_xive_alloc_vp_block.

E.g., starting then stopping 4 KVM guests gives the following pattern
in the host:

  opal_xive_alloc_vp_block(5)=0x45000020
  opal_xive_alloc_vp_block(5)=0x45000040
  opal_xive_alloc_vp_block(5)=0x45000060
  opal_xive_alloc_vp_block(5)=0x45000080
  opal_xive_free_vp_block(0x45000020)=-1
  opal_xive_free_vp_block(0x45000040)=0
  opal_xive_free_vp_block(0x45000060)=-1
  opal_xive_free_vp_block(0x45000080)=0

Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
 hw/xive.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/xive.c b/hw/xive.c
index 26edd669..4fd8a301 100644
--- a/hw/xive.c
+++ b/hw/xive.c
@@ -4463,12 +4463,14 @@ static int64_t opal_xive_free_vp_block(uint64_t vp_base)
 		return OPAL_PARAMETER;
 	if (order < (xive_chips_alloc_bits + 1))
 		return OPAL_PARAMETER;
+	if (idx & ((1 << (order - xive_chips_alloc_bits)) - 1))
+		return OPAL_PARAMETER;
 #else
 	if (order < 1)
 		return OPAL_PARAMETER;
-#endif
 	if (idx & ((1 << order) - 1))
 		return OPAL_PARAMETER;
+#endif
 
 	count = 1 << order;
 	for (i = 0; i < count; i++) {
-- 
2.13.3