Re: [PATCH 0/4] xen/arm: Unbreak ACPI

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 14 Oct 2020, Julien Grall wrote:
> Hi Elliot,
> 
> On 14/10/2020 02:37, Elliott Mitchell wrote:
> > On Tue, Oct 13, 2020 at 06:06:26PM -0700, Stefano Stabellini wrote:
> > > On Mon, 12 Oct 2020, Elliott Mitchell wrote:
> > > > I'm on different hardware, but some folks have setup Tianocore for it.
> > > > According to Documentation/arm64/acpi_object_usage.rst,
> > > > "Required: DSDT, FADT, GTDT, MADT, MCFG, RSDP, SPCR, XSDT".  Yet when
> > > > booting a Linux kernel directly on the hardware it lists APIC, BGRT,
> > > > CSRT, DSDT, DBG2, FACP, GTDT, PPTT, RSDP, and XSDT.
> > > > 
> > > > I don't know whether Linux's ACPI code omits mention of some required
> > > > tables and merely panics if they're absent.  Yet I'm speculating the
> > > > list
> > > > of required tables has shrunk, SPCR is no longer required, and the
> > > > documentation is out of date.  Perhaps SPCR was required in early Linux
> > > > ACPI implementations, but more recent ones removed that requirement?
> > > 
> > > I have just checked and SPCR is still a mandatory table in the latest
> > > SBBR specification. It is probably one of those cases where the firmware
> > > claims to be SBBR compliant, but it is not, and it happens to work with
> > > Linux.
> > 
> > Is meeting the SBBR specification supposed to be a requirement of running
> > Xen-ARM?
> 
> This is not my goal. We should try to get Xen running everywhere as long as
> this doesn't require a lot of extra code. IOW, don't ask me to review/accept a
> port of Xen to RPI3 ;).

I agree with Julien's statement.

For context, my previous comment in regards to SBBR was because I am
positive that Masami's platform is expected to be SBBR compliant.