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



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?


I am open to discussion on what the default should be, but there needs
to be a way to disable ACPI.

Agree with that.

--
Julien Grall

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