netdev - Re: [PATCH bpf-next] selftests/xsk: fix munmap for hugepage allocated umem

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Message-ID: <CAHApi-=_=ia8Pa23QRchxdx-ekPTgT5nYj=ktYGO4gRwP0cvCA@mail.gmail.com>
Date:   Thu, 20 Apr 2023 00:06:04 +0200
From:   Kal Cutter Conley <kal.conley@...tris.com>
To:     Magnus Karlsson <magnus.karlsson@...il.com>
Cc:     magnus.karlsson@...el.com, bjorn@...nel.org, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        maciej.fijalkowski@...el.com, tirthendu.sarkar@...el.com,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next] selftests/xsk: fix munmap for hugepage allocated umem

> @@ -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;
> +       }

MAP_HUGE_2MB should be ORed into mmap_flags. The offset argument
should be zero for MAP_ANONYMOUS mappings. The tests may still fail if
the default hugepage size is not 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);
>

-Kal