Re: [Xen-devel] [PATCH RESEND 05/14] libxl/arm: Construct ACPI GTDT table

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 6 Jun 2016, Julien Grall wrote:
> Hello,
> 
> On 06/06/16 13:04, Stefano Stabellini wrote:
> > On Mon, 6 Jun 2016, Julien Grall wrote:
> > > On 06/06/16 12:40, Stefano Stabellini wrote:
> > > > On Tue, 31 May 2016, Shannon Zhao wrote:
> > > > > From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> > > > 
> > > > ACPI tables for ARM guests should be user configurable: acpi=1 in the VM
> > > > config file enables them, with default off.
> > > 
> > > The VM system specification for ARM [1] mandates that both ACPI and DT
> > > should
> > > be provided and described the entire VM and its peripheral (see the
> > > section
> > > "Hardware Description").
> > > 
> > > Furthermore, the user may not know if the guest OS will use ACPI or DT For
> > > instance Redhat is using ACPI whilst Debian is using DT.
> > > 
> > > So we have to provide both by default. However, 32-bit domain should only
> > > have
> > > Device-Tree table created.
> > > 
> > > Anyway, the reason should have been described in the commit message. I
> > > would
> > > split this patch in two: introducing prepare ACPI and then GTDT table. So
> > > we
> > > can provide details in the commit message.
> > 
> > All right, let me rephrase then: we should have a VMSPEC=on or off to
> > enable or disable compliance with the VM system specification for ARM.
> > (The good thing about specifications is that there are so many to choose
> > from.) With compliance disabled, we can avoid introducing ACPI tables
> > for the guest.
> > 
> > Given that "VMSPEC" is cumbersome, I suggest to introduce a simpler and
> > more meaningful alias: "ACPI" :-)
> 
> The VM specification introduces other components such as a SBSA UART emulation
> (which is not yet implemented by Xen).
> 
> Do we want an option for each components?

This is a good point. If one wants to avoid ACPI then she probably would
want to avoid SBSA UART emulation too. So maybe after all it might be
better to have a single

vm_system_spec=1/0

option? I am OK with both having multiple options or just one.

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