2024-03-08 12:07:41

by Puranjay Mohan

Subject: [PATCH bpf-next] bpf: cap BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

On some architectures like ARM64, PMD_SIZE can be really large in some
configurations. Like with CONFIG_ARM64_64K_PAGES=y the PMD_SIZE is
512MB.

Use 2MB * num_possible_nodes() as the upper limit for allocations done
through the prog pack allocator.

Fixes: ea2babac63d4 ("bpf: Simplify bpf_prog_pack_[size|mask]")
Reported-by: "kernelci.org bot" <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Suggested-by: Song Liu <[email protected]>
Signed-off-by: Puranjay Mohan <[email protected]>
---
kernel/bpf/core.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 134b7979f537..83a3b6964e54 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -893,8 +893,17 @@ static LIST_HEAD(pack_list);
* CONFIG_MMU=n. Use PAGE_SIZE in these cases.
*/
#ifdef PMD_SIZE
+/*
+ * PMD_SIZE is really big for some archs. It doesn't make sense to
+ * reserve too much memory in one allocation. Cap BPF_PROG_PACK_SIZE to
+ * 2MiB * num_possible_nodes().
+ */
+#if PMD_SIZE <= (1 << 21)
#define BPF_PROG_PACK_SIZE (PMD_SIZE * num_possible_nodes())
#else
+#define BPF_PROG_PACK_SIZE ((1 << 21) * num_possible_nodes())
+#endif
+#else
#define BPF_PROG_PACK_SIZE PAGE_SIZE
#endif

--
2.40.1

2024-03-08 16:55:36

by Song Liu

Subject: Re: [PATCH bpf-next] bpf: cap BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

On Fri, Mar 8, 2024 at 4:07 AM Puranjay Mohan <[email protected]> wrote:
>
> On some architectures like ARM64, PMD_SIZE can be really large in some
> configurations. Like with CONFIG_ARM64_64K_PAGES=y the PMD_SIZE is
> 512MB.
>
> Use 2MB * num_possible_nodes() as the upper limit for allocations done
> through the prog pack allocator.
>
> Fixes: ea2babac63d4 ("bpf: Simplify bpf_prog_pack_[size|mask]")
> Reported-by: "kernelci.org bot" <[email protected]>
> Closes: https://lore.kernel.org/all/[email protected]/
> Suggested-by: Song Liu <[email protected]>
> Signed-off-by: Puranjay Mohan <[email protected]>
> ---
> kernel/bpf/core.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 134b7979f537..83a3b6964e54 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -893,8 +893,17 @@ static LIST_HEAD(pack_list);
> * CONFIG_MMU=n. Use PAGE_SIZE in these cases.
> */
> #ifdef PMD_SIZE
> +/*
> + * PMD_SIZE is really big for some archs. It doesn't make sense to
> + * reserve too much memory in one allocation. Cap BPF_PROG_PACK_SIZE to
> + * 2MiB * num_possible_nodes().
> + */

In BPF code, we prefer a different style of multiple line comments:

/* PMD_SIZE is really big for some archs. It doesn't make sense to
* reserve too much memory in one allocation. Cap BPF_PROG_PACK_SIZE to
* 2MiB * num_possible_nodes().
*/

Other than this, this looks good to me.

Acked-by: Song Liu <[email protected]>

Thanks,
Song

> +#if PMD_SIZE <= (1 << 21)
> #define BPF_PROG_PACK_SIZE (PMD_SIZE * num_possible_nodes())
> #else
> +#define BPF_PROG_PACK_SIZE ((1 << 21) * num_possible_nodes())
> +#endif
> +#else
> #define BPF_PROG_PACK_SIZE PAGE_SIZE
> #endif

2024-03-08 23:13:50

by Alexei Starovoitov

Subject: Re: [PATCH bpf-next] bpf: cap BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

On Fri, Mar 8, 2024 at 8:55 AM Song Liu <[email protected]> wrote:
>
> On Fri, Mar 8, 2024 at 4:07 AM Puranjay Mohan <[email protected]> wrote:
> >
> > On some architectures like ARM64, PMD_SIZE can be really large in some
> > configurations. Like with CONFIG_ARM64_64K_PAGES=y the PMD_SIZE is
> > 512MB.
> >
> > Use 2MB * num_possible_nodes() as the upper limit for allocations done
> > through the prog pack allocator.
> >
> > Fixes: ea2babac63d4 ("bpf: Simplify bpf_prog_pack_[size|mask]")
> > Reported-by: "kernelci.org bot" <[email protected]>
> > Closes: https://lore.kernel.org/all/[email protected]/
> > Suggested-by: Song Liu <[email protected]>
> > Signed-off-by: Puranjay Mohan <[email protected]>
> > ---
> > kernel/bpf/core.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> > index 134b7979f537..83a3b6964e54 100644
> > --- a/kernel/bpf/core.c
> > +++ b/kernel/bpf/core.c
> > @@ -893,8 +893,17 @@ static LIST_HEAD(pack_list);
> > * CONFIG_MMU=n. Use PAGE_SIZE in these cases.
> > */
> > #ifdef PMD_SIZE
> > +/*
> > + * PMD_SIZE is really big for some archs. It doesn't make sense to
> > + * reserve too much memory in one allocation. Cap BPF_PROG_PACK_SIZE to
> > + * 2MiB * num_possible_nodes().
> > + */
>
> In BPF code, we prefer a different style of multiple line comments:
>
> /* PMD_SIZE is really big for some archs. It doesn't make sense to
> * reserve too much memory in one allocation. Cap BPF_PROG_PACK_SIZE to
> * 2MiB * num_possible_nodes().
> */

Fixed up while applying. Thanks everyone.