xdp: xdp_umem: fix umem pages mapping for 32bits systems

Use kmap instead of page_address as it's not always in low memory.
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

net/xdp/xdp_umem.c

@@ -14,6 +14,7 @@
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
 #include <linux/idr.h>
+#include <linux/highmem.h>
 
 #include "xdp_umem.h"
 #include "xsk_queue.h"
@@ -164,6 +165,14 @@ void xdp_umem_clear_dev(struct xdp_umem *umem)
 	umem->zc = false;
 }
 
+static void xdp_umem_unmap_pages(struct xdp_umem *umem)
+{
+	unsigned int i;
+
+	for (i = 0; i < umem->npgs; i++)
+		kunmap(umem->pgs[i]);
+}
+
 static void xdp_umem_unpin_pages(struct xdp_umem *umem)
 {
 	unsigned int i;
@@ -207,6 +216,7 @@ static void xdp_umem_release(struct xdp_umem *umem)
 
 	xsk_reuseq_destroy(umem);
 
+	xdp_umem_unmap_pages(umem);
 	xdp_umem_unpin_pages(umem);
 
 	kfree(umem->pages);
@@ -369,7 +379,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	}
 
 	for (i = 0; i < umem->npgs; i++)
-		umem->pages[i].addr = page_address(umem->pgs[i]);
+		umem->pages[i].addr = kmap(umem->pgs[i]);
 
 	return 0;