[RFC 05/27] vhost: add helper for IOTLB entries shared page check

[Maxime Coquelin]

This patch introduces a helper to check whether two IOTLB
entries share a page.

Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
 lib/vhost/iotlb.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/lib/vhost/iotlb.c b/lib/vhost/iotlb.c
index e8f1cb661e..d919f74704 100644
--- a/lib/vhost/iotlb.c
+++ b/lib/vhost/iotlb.c
@@ -23,6 +23,23 @@ struct vhost_iotlb_entry {
 
 #define IOTLB_CACHE_SIZE 2048
 
+static bool
+vhost_user_iotlb_share_page(struct vhost_iotlb_entry *a, struct 
vhost_iotlb_entry *b,
+               uint64_t align)
+{
+       uint64_t a_end, b_start;
+
+       if (a == NULL || b == NULL)
+               return false;
+
+       /* Assumes entry a lower than entry b */
+       RTE_ASSERT(a->uaddr < b->uaddr);
+       a_end = RTE_ALIGN_CEIL(a->uaddr + a->size, align);
+       b_start = RTE_ALIGN_FLOOR(b->uaddr, align);
+
+       return a_end > b_start;
+}
+
 static void
 vhost_user_iotlb_set_dump(struct virtio_net *dev, struct vhost_iotlb_entry 
*node)
 {
@@ -37,16 +54,14 @@ static void
 vhost_user_iotlb_clear_dump(struct virtio_net *dev, struct vhost_iotlb_entry 
*node,
                struct vhost_iotlb_entry *prev, struct vhost_iotlb_entry *next)
 {
-       uint64_t align, mask;
+       uint64_t align;
 
        align = hua_to_alignment(dev->mem, (void *)(uintptr_t)node->uaddr);
-       mask = ~(align - 1);
 
        /* Don't disable coredump if the previous node is in the same page */
-       if (prev == NULL || (node->uaddr & mask) != ((prev->uaddr + prev->size 
- 1) & mask)) {
+       if (!vhost_user_iotlb_share_page(prev, node, align)) {
                /* Don't disable coredump if the next node is in the same page 
*/
-               if (next == NULL ||
-                               ((node->uaddr + node->size - 1) & mask) != 
(next->uaddr & mask))
+               if (!vhost_user_iotlb_share_page(node, next, align))
                        mem_set_dump((void *)(uintptr_t)node->uaddr, 
node->size, false, align);
        }
 }
-- 
2.39.2