diff --git a/share/man/man9/pmap_kextract.9 b/share/man/man9/pmap_kextract.9
--- a/share/man/man9/pmap_kextract.9
+++ b/share/man/man9/pmap_kextract.9
@@ -31,9 +31,21 @@
 function retrieves the underlying physical memory address corresponding to the
 given kernel virtual address
 .Fa va .
-The value of
+The caller is responsible for ensuring that
 .Fa va
-must belong to a valid mapping in the kernel address space.
+belongs to a valid mapping in the kernel address space.
+The returned physical address is only meaningful as long as the mapping remains
+stable, so the caller must also have some knowledge or guarantee of the
+mapping's lifetime.
+For example, it is invalid to call
+.Fn pmap_kextract
+with the address of a malloc'd object while there is a possibility for that
+object to be freed concurrently.
+.Pp
+Unlike
+.Xr pmap_extract 9 ,
+.Fn pmap_kextract
+is safe to be called from any context; it has no internal locking or sleep.
 .Pp
 .Fn vtophys
 is an alias for
@@ -42,7 +54,7 @@
 .Sh RETURN VALUES
 The
 .Fn pmap_kextract
-function returns the address of physical memory mapped at the kernel
+function returns the physical address of memory mapped at the kernel
 virtual address
 .Fa va .
 .Pp