Re: [PATCH v2 10/10] tcg/loongarch64: Reorg goto_tb implementation

[WANG Xuerui <i.qemu@xen0n.name>]

On 1/18/23 09:11, Richard Henderson wrote:
> The old implementation replaces two insns, swapping between
>
>          b       <dest>
>          nop
> and
>          pcaddu18i tmp, <dest>
>          jirl      zero, tmp, <dest> & 0xffff
>
> There is a race condition in which a thread could be stopped at
> the jirl, i.e. with the top of the address loaded, and when
> restarted we have re-linked to a different TB, so that the top
> half no longer matches the bottom half.
>
> Note that while we never directly re-link to a different TB, we
> can link, unlink, and link again all while the stopped thread
> remains stopped.
>
> The new implementation replaces only one insn, swapping between
>
>          b       <dest>
> and
>          pcadd   tmp, <jmp_addr>
>
> falling through to load the address from tmp, and branch.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   tcg/loongarch64/tcg-target.h     |  7 +---
>   tcg/loongarch64/tcg-target.c.inc | 72 ++++++++++++++------------------
>   2 files changed, 33 insertions(+), 46 deletions(-)

I've tested this on my 3A5000 box and things seem to work, thanks.

Reviewed-by: WANG Xuerui <git@xen0n.name>