vhost: correctly set bits of dirty pages

Fix two bugs in dirty page logging:
When counting pages we should increase address by 1 instead of
VHOST_PAGE_SIZE. Make log_write() correctly process requests
that cross pages with write_address not starting at page boundary.

Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 916cdbc279e0..4c256d15c249 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -885,6 +885,7 @@ static int log_write(void __user *log_base,
         int r;
         if (!write_length)
                 return 0;
+        write_length += write_address % VHOST_PAGE_SIZE;
         write_address /= VHOST_PAGE_SIZE;
         for (;;) {
                 u64 base = (u64)(unsigned long)log_base;
@@ -898,7 +899,7 @@ static int log_write(void __user *log_base,
                 if (write_length <= VHOST_PAGE_SIZE)
                         break;
                 write_length -= VHOST_PAGE_SIZE;
-                write_address += VHOST_PAGE_SIZE;
+                write_address += 1;
         }
         return r;
 }