selftests/xsk: Fix munmap for hugepage allocated umem

Fix the unmapping of hugepage allocated umems so that they are
properly unmapped. The new test referred to in the fixes label,
introduced a test that allocated a umem that is not a multiple of a 2M
hugepage size. This is fine for mmap() that rounds the size up the
nearest multiple of 2M. But munmap() requires the size to be a
multiple of the hugepage size in order for it to unmap the region. The
current behaviour of not properly unmapping the umem, was discovered
when further additions of tests that require hugepages (unaligned mode
tests only) started failing as the system was running out of
hugepages.

Fixes: c080159 ("selftests: xsk: Add test UNALIGNED_INV_DESC_4K1_FRAME_SIZE")
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230418143617.27762-1-magnus.karlsson@gmail.com

tools/testing/selftests/bpf/xskxceiver.c

@@ -77,6 +77,7 @@
 #include <linux/if_link.h>
 #include <linux/if_ether.h>
 #include <linux/ip.h>
+#include <linux/mman.h>
 #include <linux/udp.h>
 #include <arpa/inet.h>
 #include <net/if.h>
@@ -1286,16 +1287,19 @@ static void thread_common_ops(struct test_spec *test, struct ifobject *ifobject)
 	u64 umem_sz = ifobject->umem->num_frames * ifobject->umem->frame_size;
 	int mmap_flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE;
 	LIBBPF_OPTS(bpf_xdp_query_opts, opts);
+	off_t mmap_offset = 0;
 	void *bufs;
 	int ret;
 
-	if (ifobject->umem->unaligned_mode)
+	if (ifobject->umem->unaligned_mode) {
 		mmap_flags |= MAP_HUGETLB;
+		mmap_offset = MAP_HUGE_2MB;
+	}
 
 	if (ifobject->shared_umem)
 		umem_sz *= 2;
 
-	bufs = mmap(NULL, umem_sz, PROT_READ | PROT_WRITE, mmap_flags, -1, 0);
+	bufs = mmap(NULL, umem_sz, PROT_READ | PROT_WRITE, mmap_flags, -1, mmap_offset);
 	if (bufs == MAP_FAILED)
 		exit_with_error(errno);
 
@@ -1379,13 +1383,19 @@ static void *worker_testapp_validate_rx(void *arg)
 	pthread_exit(NULL);
 }
 
+static u64 ceil_u64(u64 a, u64 b)
+{
+	return (a + b - 1) / b;
+}
+
 static void testapp_clean_xsk_umem(struct ifobject *ifobj)
 {
 	u64 umem_sz = ifobj->umem->num_frames * ifobj->umem->frame_size;
 
 	if (ifobj->shared_umem)
 		umem_sz *= 2;
 
+	umem_sz = ceil_u64(umem_sz, HUGEPAGE_SIZE) * HUGEPAGE_SIZE;
 	xsk_umem__delete(ifobj->umem->umem);
 	munmap(ifobj->umem->buffer, umem_sz);
 }
@@ -1619,14 +1629,15 @@ static void testapp_stats_fill_empty(struct test_spec *test)
 /* Simple test */
 static bool hugepages_present(struct ifobject *ifobject)
 {
-	const size_t mmap_sz = 2 * ifobject->umem->num_frames * ifobject->umem->frame_size;
+	size_t mmap_sz = 2 * ifobject->umem->num_frames * ifobject->umem->frame_size;
 	void *bufs;
 
 	bufs = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE,
-		    MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
+		    MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, MAP_HUGE_2MB);
 	if (bufs == MAP_FAILED)
 		return false;
 
+	mmap_sz = ceil_u64(mmap_sz, HUGEPAGE_SIZE) * HUGEPAGE_SIZE;
 	munmap(bufs, mmap_sz);
 	return true;
 }

tools/testing/selftests/bpf/xskxceiver.h

@@ -56,6 +56,7 @@
 #define RX_FULL_RXQSIZE 32
 #define UMEM_HEADROOM_TEST_SIZE 128
 #define XSK_UMEM__INVALID_FRAME_SIZE (XSK_UMEM__DEFAULT_FRAME_SIZE + 1)
+#define HUGEPAGE_SIZE (2 * 1024 * 1024)
 
 #define print_verbose(x...) do { if (opt_verbose) ksft_print_msg(x); } while (0)