Re: [PATCH bpf-next 0/4] Add internal-only BPF per-CPU instructions

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2024-03-29 at 11:47 -0700, Andrii Nakryiko wrote:
> Add two new BPF instructions for dealing with per-CPU memory.
> 
> One, BPF_LDX | BPF_ADDR_PERCPU | BPF_DW (where BPF_ADD_PERCPU is unused
> 0xe0 opcode), resolved provided per-CPU address (offset) to an absolute
> address where per-CPU data resides for "this" CPU. This is the most universal,
> and, strictly speaking, the only per-CPU BPF instruction necessary.
> 
> I also added BPF_LDX | BPF_MEM_PERCPU | BPF_{B,H,W,DW} (BPF_MEM_PERCPU using
> another unused 0xc0 opcode), which can be considered an optimization
> instruction, which allows to *read* per-CPU data up to 8 bytes in one
> instruction, without having to first resolve the address and then
> dereferencing the memory. This one is used in inlining of
> bpf_get_smp_processor_id(), but it would be fine to implement the latter with
> BPF_ADD_PERCPU, followed by normal BPF_LDX | BPF_MEM, so I'm fine dropping
> this one, if requested.

Hi Andrii,

I've read through the series and it looks good
(modulo architecture related issues reported by CI).

Thanks,
Eduard