Re: [PATCH V3 6/6] dt-bindings: xen: Clarify "reg" purpose

[Oleksandr <olekstysh@xxxxxxxxx>]

On 25.11.21 03:09, Stefano Stabellini wrote:

Hi Stefano

> On Wed, 24 Nov 2021, Oleksandr Tyshchenko wrote:
> > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> >
> > Xen on Arm has gained new support recently to calculate and report
> > extended regions (unused address space) safe to use for external
> > mappings. These regions are reported via "reg" property under
> > "hypervisor" node in the guest device-tree. As region 0 is reserved
> > for grant table space (always present), the indexes for extended
> > regions are 1...N.
> >
> > No device-tree bindings update is needed (except clarifying the text)
> > as guest infers the presence of extended regions from the number
> > of regions in "reg" property.
> >
> > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> > ---
> > According to the recent update to Xen's guest.txt:
> > https://xenbits.xen.org/gitweb/?p=xen.git;a=blob_plain;f=docs/misc/arm/device-tree/guest.txt;hb=refs/heads/master
> >
> > Changes V2 -> V3:
> >     - new patch
> > ---
> >   Documentation/devicetree/bindings/arm/xen.txt | 12 ++++++++----
> >   1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/arm/xen.txt 
> > b/Documentation/devicetree/bindings/arm/xen.txt
> > index db5c56d..156fe10b 100644
> > --- a/Documentation/devicetree/bindings/arm/xen.txt
> > +++ b/Documentation/devicetree/bindings/arm/xen.txt
> > @@ -7,10 +7,14 @@ the following properties:
> >         compatible = "xen,xen-<version>", "xen,xen";
> >     where <version> is the version of the Xen ABI of the platform.
> >   
> > -- reg: specifies the base physical address and size of a region in
> > -  memory where the grant table should be mapped to, using an
> > -  HYPERVISOR_memory_op hypercall. The memory region is large enough to map
> > -  the whole grant table (it is larger or equal to gnttab_max_grant_frames()).
> > +- reg: specifies the base physical address and size of the regions in memory
> > +  where the special resources should be mapped to, using an 
> > HYPERVISOR_memory_op
> > +  hypercall.
> > +  Region 0 is reserved for mapping grant table, it must be always present.
> > +  The memory region is large enough to map the whole grant table (it is larger
> > +  or equal to gnttab_max_grant_frames()).
> > +  Regions 1...N are extended regions (unused address space) for mapping foreign
> > +  GFNs and grants, they might be absent if there is nothing to expose.
> >     This property is unnecessary when booting Dom0 using ACPI.
> I would remove the last sentence about ACPI as the initialization is not
> done via the xen,xen device tree node in that case anyway.
Agree, will do. I assume, the similar sentence for the "interrupts" 
property down the text wants removing as well.

> With that change:
>
> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Thanks!


--
Regards,

Oleksandr Tyshchenko