bpf: cap BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

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

Posted by Puranjay Mohan 1 year, 11 months ago

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" <bot@kernelci.org>
Closes: https://lore.kernel.org/all/7e216c88-77ee-47b8-becc-a0f780868d3c@sirena.org.uk/
Suggested-by: Song Liu <song@kernel.org>
Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
---
 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

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

Posted by Song Liu 1 year, 11 months ago

On Fri, Mar 8, 2024 at 4:07 AM Puranjay Mohan <puranjay12@gmail.com> 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" <bot@kernelci.org>
> Closes: https://lore.kernel.org/all/7e216c88-77ee-47b8-becc-a0f780868d3c@sirena.org.uk/
> Suggested-by: Song Liu <song@kernel.org>
> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> ---
>  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 <song@kernel.org>

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

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

Posted by Alexei Starovoitov 1 year, 11 months ago

On Fri, Mar 8, 2024 at 8:55 AM Song Liu <song@kernel.org> wrote:
>
> On Fri, Mar 8, 2024 at 4:07 AM Puranjay Mohan <puranjay12@gmail.com> 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" <bot@kernelci.org>
> > Closes: https://lore.kernel.org/all/7e216c88-77ee-47b8-becc-a0f780868d3c@sirena.org.uk/
> > Suggested-by: Song Liu <song@kernel.org>
> > Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> > ---
> >  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.