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Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen

On 2015/8/4 22:43, Christoffer Dall wrote:
Hi Shannon,

On Tue, Aug 4, 2015 at 3:43 PM, Shannon Zhao <zhaoshenglong@xxxxxxxxxx> wrote:
This document is going to explain the design details of Xen booting with
ACPI on ARM. Maybe parts of it may not be appropriate. Any comments are

To Xen itself booting with ACPI, this is similar to Linux kernel except
that Xen doesn't parse DSDT table. So I'll skip this part and focus on
how Xen prepares ACPI tables for DOM0 and how Xen passes them to DOM0.

1)copy and change some EFI and ACPI tables.
   a) Copy EFI_SYSTEM_TABLE and change the value of FirmwareVendor,
      VendorGuid, VendorTable, ConfigurationTable. These changes are not
      very special and it just assign values to these members.
   b) Create EFI_MEMORY_DESCRIPTOR table. This will add memory start and
      size information of DOM0. And DOM0 will get the memory information
      through this EFI table.

Are the tables above EFI tables and all the tables below ACPI tables?

IIUC, the location of these tables doesn't matter. Because DOM0 gets the EFI table info through DT and get ACPI tables through RSDP pointer.

   c) Copy FADT table. Change the value of arm_boot_flags to enable PSCI
      and HVC. Let the hypervisor_id be "XenVMM" in order to tell DOM0
      that it runs on Xen hypervisor, so DOM0 can call hypercall to get
      some informations for booting necessity, such as grant tab start
      address and size. Change header revison, length and checksum as
   d) Copy GTDT table. Set non_secure_el2_interrupt and
      non_secure_el2_flags to 0 to mask EL2 timer for DOM0.

Is this necessary, doesn't Linux notice that it's booted in EL1 and
will ignore everything related to EL2?

Yes, it's maybe not necessary.

   e) Copy MADT table. According to the value of dom0_max_vcpus to change
      the number GICC entries.
   f) Create STAO table. This table is a new added one that's used to
      define a list of ACPI namespace names that are to be ignored by the
      OSPM in DOM0. Currently we use it to tell OSPM should ignore UART
      defined in SPCR table.
   g) Copy XSDT table. Add a new table entry for STAO and change other
      table's entries.
   h) Change the value of xsdt_physical_address in RSDP table.
   i) The reset of tables are not copied or changed. They are reused

s/reset/rest/ ?




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