Re: Platform specification questions


On Mon, Dec 13, 2021 at 8:30 AM Anup Patel <anup@...> wrote:
On Mon, Dec 13, 2021 at 6:46 PM Ved Shanbhogue <ved@...> wrote:
> Hi Anup
> On Mon, Dec 13, 2021 at 09:25:43AM +0530, Anup Patel wrote:
> >>
> >> Section
> >> "Software interrupts for M-mode, HS-mode and VS-mode are supported using AIA IMSIC devices". Is the term "software interrupt" here intended to be the minor identities 3, 1, and 2? If so please clarify what the support in IMSIC is expected to be for these minor identities.
> >I think the confusion here is because the RISC-V platform
> >specification uses the term "software interrupt" for both
> >"inter-processor interrupt" and "minor identities 3, 1, and 2". I
> >suggest using the term "inter-processor interrupt" at most places and
> >only use the term "software interrupt" in-context of ACLINT MSWI or
> >SSWI devices.
> >
> Yes, that was my conclusion that "software interrupt" here was used to mean an IPI. I think clearing this up would be helpful.
> >>
> >> Section
> >> Is supporting SBI TIME optional if the server extension is supported as server extension requires Sstc? Is supporting SBI IPI optional if AiA IMSIC is supported?
> >
> >I agree, this text needs to be improved because now Base and Server
> >are separate platforms. Since, the Server platform mandates IMSIC and
> >Priv Sstc extension so SBI TIME, IPI and RFENCE can be optional but
> >this is not true for the Base platform.
> >
> Yes, however the Server is additived to the base as written. Even for base, if Sstc and IMSIC are supported then SBI TIME, IPI, and RFENCE can be optional.

The current text/organization is going to change (as discussed in
previous meetings). The Server platform will be a separate platform
independent of the Base platform because some of the requirements will
be different for both platforms. (@Kumar/Atish please add if I missed

For the Base platform, I agree we can make SBI TIME, IPI and RFENCE
mandatory only when IMSIC and Sstc is not present. (@Atish do you
recall any other rationale in this context ?)

We should have a table with dependencies for SBI extensions. E.g.
SBI Time only required if sstc is not present
SBI IPI/RFENCE is only required if IMSIC or SSWI is not present

I will send a patch after the spec is broken into separate platforms (OS-A server and OS-A embedded)

> regards
> ved

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