Re: [PATCH v3 6/7] riscv: add a data fence for CMODX in the kernel mode

Andrea Parri
2025-03-11T18:32:12Z

On Tue, Mar 11, 2025 at 03:53:36PM +0100, Björn Töpel wrote:
> Andrea Parri <parri.andrea@gmail.com> writes:
>
> >> FWIW, the for S-IMSIC the write is already writel(), so we'll have the
> >> text patching and IPI ordered. Regardless, there's more than one flavor
> >> of IPI on RISC-V!
> >
> > AFAIU, this writel() is intended to order the insertion (and the initialization)
> > of the CSD object before the MMIO writes; so, the "right fix" seems to turn the
> > "other flavors" into using a writel() or providing a similar ordering guarantee.
>
> Yes, that's probably the right approach, or maybe follow-up!
>
> > As a bonus, such change should address/fix all current and future occurrences of
> > the message-passing scenario in question (the patch addressed the occurrence in
> > flush_icache_all(), but there appears to be a similar one in flush_icache_mm()).
>
> Indeed. I wonder if the SBI remote fence.i needs it?

Ah! So I am not alone: AFAICT, that remains a matter of discussions with your SEE
team/developers. :-|

Andrea