Re: [Xen-devel] [PATCH v2 26/41] arm : acpi add xen environment table

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 28 May 2015, Jan Beulich wrote:
> >>> On 28.05.15 at 14:12, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Thu, 28 May 2015, Jan Beulich wrote:
> >> >>> On 28.05.15 at 12:58, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >> > Let's take a closer look at this table. After the boilierplate, these
> >> > are the interesting fields:
> >> > 
> >> > GNT Start, GNT Size
> >> > Evtchn Intr, Evtchn Intr Flags
> >> > 
> >> > After the table, it is clearly stated:
> >> > 
> >> > "The Grant Table region is optional."
> >> > 
> >> > and
> >> > 
> >> > "The Event Channel Interrupt is optional."
> >> > 
> >> > So I think there is no problem: we don't want to pass any info in that
> >> > table? Sure, let's not pass any. We can still use it to flag the
> >> > presence of Xen on the platform.
> >> 
> >> Even more so a reason to use what base ACPI has, without any
> >> custom table.
> > 
> > Could you please make a concrete suggestion with table names and fields?
> 
> I already pointed you at 6.0's new FADT field "Hypervisor Vendor
> Identity".

OK, that is a decent alternative.

We don't have a suitable hypercall to retrieve the evtchn PPI but we
could add one. Overall I still prefer the table approach, but if you
really don't want it, I can live with the hypercalls.

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