Re: Watchdog Spec Questions

Greg Favor

On Tue, Apr 19, 2022 at 4:48 PM Phil McCoy <pnm@...> wrote:
Several modifications to the WDT spec were proposed, and seemingly agreed in this discussion thread.  Is there any plan to actually update the spec?  Should I try to learn enough git-foo to generate a pull request?

Any plans to try to get this ratified in the foreseeable future?

I wouldn't say there was true convergence on a near-final hardware WDT spec.  To start with there have also been arguments to abstract any hardware away from what S/HS-mode sees and to instead have an OS/hypervisor do SBI calls to set up its watchdog and to "refresh" the watchdog, and it could receive some form of callback on a first-stage watchdog timeout.  This is based on the frequency of watchdog refreshes being relatively very low and not anywhere close to a performance overhead issue.

In any case, proper discussion and resolution of this issue should happen in the OS-A SEE TG (whether that results in a RISC-V hardware standard like in ARM architecture or in a RISC-V SBI standard extension).



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