Re: [PATCH bpf-next v5 09/11] bpf: Add bitwise atomic instructions

[Yonghong Song]

On 12/15/20 4:18 AM, Brendan Jackman wrote:
> This adds instructions for
>
> atomic[64]_[fetch_]and
> atomic[64]_[fetch_]or
> atomic[64]_[fetch_]xor
>
> All these operations are isomorphic enough to implement with the same
> verifier, interpreter, and x86 JIT code, hence being a single commit.
>
> The main interesting thing here is that x86 doesn't directly support
> the fetch_ version these operations, so we need to generate a CMPXCHG
> loop in the JIT. This requires the use of two temporary registers,
> IIUC it's safe to use BPF_REG_AX and x86's AUX_REG for this purpose.
>
> Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>

Acked-by: Yonghong Song <yhs@xxxxxx>