Re: [PATCH v2 1/2] docs: fusa: Define the requirements for XEN_VERSION hypercall.

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

On 27/02/2025 17:15, Bertrand Marquis wrote:
> Hi Ayan,
Hi Bertrand,

I have just some clarifications.

> > On 27 Feb 2025, at 16:09, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx> wrote:
> >
> > In the current patch, we have defined the requirements which are common for
> > all the commands.
> >
> > Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> > ---
> > Changes from -
> >
> > v1 - 1. Fixed `XenProd~version_hyp_ret_val~1` requirement as Xen does not return
> > 0 for success in all the cases.
> > 2. Reworded the requirements so as to write them from Xen's perspective (not
> > domain's perspective).
> >
> > .../fusa/reqs/design-reqs/arm64/hypercall.rst | 55 +++++++++++++++++
> > docs/fusa/reqs/index.rst                      |  2 +
> > docs/fusa/reqs/market-reqs/reqs.rst           | 16 +++++
> > .../reqs/product-reqs/version_hypercall.rst   | 61 +++++++++++++++++++
> > 4 files changed, 134 insertions(+)
> > create mode 100644 docs/fusa/reqs/design-reqs/arm64/hypercall.rst
> > create mode 100644 docs/fusa/reqs/product-reqs/version_hypercall.rst
> >
> > diff --git a/docs/fusa/reqs/design-reqs/arm64/hypercall.rst 
> > b/docs/fusa/reqs/design-reqs/arm64/hypercall.rst
> > new file mode 100644
> > index 0000000000..ffd883260c
> > --- /dev/null
> > +++ b/docs/fusa/reqs/design-reqs/arm64/hypercall.rst
> > @@ -0,0 +1,55 @@
> > +.. SPDX-License-Identifier: CC-BY-4.0
> > +
> > +Hypercall
> > +=========
> > +
> > +Instruction
> > +-----------
> > +
> > +`XenSwdgn~arm64_hyp_instr~1`
> > +
> > +Description:
> > +Xen shall treat domain hypercall exception as hypercall requests.
> > +
> > +Rationale:
> > +
> > +Comments:
> > +Hypercall is one of the communication mechanism between Xen and domains.
> > +Domains use hypercalls for various requests to Xen.
> > +Domains use 'hvc' instruction to invoke hypercalls.
> > +
> > +Covers:
> > + - `XenProd~version_hyp_first_param~1`
> > + - `XenProd~version_hyp_second_param~1`
> > +
> > +Parameters
> > +----------
> > +
> > +`XenSwdgn~arm64_hyp_param~1`
> > +
> > +Description:
> > +Xen shall use x0 to read the first parameter, x1 for second parameter and so
> > +on, for domain hypercall requests.
> > +
> > +Rationale:
> > +
> > +Comments:
> > +
> > +Covers:
> > + - `XenProd~version_hyp_first_param~1`
> > + - `XenProd~version_hyp_second_param~1`
> > +
> > +Return value
> > +------------
> > +
> > +`XenSwdgn~arm64_ret_val~1`
> > +
> > +Description:
> > +Xen shall store the return value in x0 register.
> > +
> > +Rationale:
> > +
> > +Comments:
> > +
> > +Covers:
> > + - `XenProd~version_hyp_ret_val~1`
> > diff --git a/docs/fusa/reqs/index.rst b/docs/fusa/reqs/index.rst
> > index 1088a51d52..d8683edce7 100644
> > --- a/docs/fusa/reqs/index.rst
> > +++ b/docs/fusa/reqs/index.rst
> > @@ -10,5 +10,7 @@ Requirements documentation
> >     market-reqs/reqs
> >     product-reqs/reqs
> >     product-reqs/arm64/reqs
> > +   product-reqs/version_hypercall
> >     design-reqs/arm64/generic-timer
> >     design-reqs/arm64/sbsa-uart
> > +   design-reqs/arm64/hypercall
> > diff --git a/docs/fusa/reqs/market-reqs/reqs.rst 
> > b/docs/fusa/reqs/market-reqs/reqs.rst
> > index 2d297ecc13..0e29fe5362 100644
> > --- a/docs/fusa/reqs/market-reqs/reqs.rst
> > +++ b/docs/fusa/reqs/market-reqs/reqs.rst
> > @@ -79,3 +79,19 @@ Comments:
> >
> > Needs:
> >   - XenProd
> > +
> > +Version hypercall
> > +-----------------
> > +
> > +`XenMkt~version_hypercall~1`
> > +
> > +Description:
> > +Xen shall provide an interface for the domains to retrieve Xen's version, type
> > +and compilation information.
> > +
> > +Rationale:
> > +
> > +Comments:
> > +
> > +Needs:
> > + - XenProd
> > diff --git a/docs/fusa/reqs/product-reqs/version_hypercall.rst 
> > b/docs/fusa/reqs/product-reqs/version_hypercall.rst
> > new file mode 100644
> > index 0000000000..03221f70c3
> > --- /dev/null
> > +++ b/docs/fusa/reqs/product-reqs/version_hypercall.rst
> > @@ -0,0 +1,61 @@
> > +.. SPDX-License-Identifier: CC-BY-4.0
> > +
> > +Version hypercall
> > +=================
> > +
> > +First Parameter
> > +---------------
> > +
> > +`XenProd~version_hyp_first_param~1`
> > +
> > +Description:
> > +Xen shall treat the first argument (as an integer) to denote the command number
> > +for the hypercall.
> You speak of argument here and parameter earlier.
> I would rephrase to: the first argument of an hypercall exception as the 
> command number for the hypercall.
Ack

Should I do this everywhere ?

s/parameter/argument

That would make it consistent.

> > +
> > +Rationale:
> > +
> > +Comments:
> > +
> > +Covers:
> > + - `XenMkt~version_hypercall~1`
> > +
> > +Needs:
> > + - XenSwdgn
> > +
> > +Second Parameter
> > +----------------
> > +
> > +`XenProd~version_hyp_second_param~1`
> > +
> > +Description:
> > +Xen shall treat the second argument as a virtual address to buffer in domain's
> > +memory.
> > +
> Same here on argument vs parameter.
>
> > +Rationale:
> > +
> > +Comments:
> > +
> > +Covers:
> > + - `XenMkt~version_hypercall~1`
> > +
> > +Needs:
> > + - XenSwdgn
> > +
> > +Return Value
> > +------------
> > +
> > +`XenProd~version_hyp_ret_val~1`
> > +
> > +Description:
> > +In case the hypercall fails, Xen shall return one of the error codes defined
> > +in 
> > http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/public/errno.h.
> This is a very imprecise req as it does not states what can fail and what 
> should be returned exactly.
> Do we want to be that generic ? if yes then this might be a requirement valid 
> for any hypercall.
Yes, you are correct.

I am thinking of pushing this further up ie have this requirement at 
market level and leave it **unlinked** to any product requirement.
IOW, we don't need to validate each and every error code returned by the 
hypercall.
Or should we just drop this requirement ?

- Ayan

> Cheers
> Bertrand
>
> > +
> > +Rationale:
> > +
> > +Comments:
> > +
> > +Covers:
> > + - `XenMkt~version_hypercall~1`
> > +
> > +Needs:
> > + - XenSwdgn
> > \ No newline at end of file
> > --
> > 2.25.1