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D42458.1794415533.diff

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

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