Re: Design doc of adding ACPI support for arm64 on Xen

[Shannon Zhao <shannon.zhao@linaro.org>]

On 2015/8/4 22:43, Christoffer Dall wrote:
> Hi Shannon,
>
> On Tue, Aug 4, 2015 at 3:43 PM, Shannon Zhao <zhaoshenglong@huawei.com> 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
>> welcome.
>>
>> 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
>>       well.
>>    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/ ?
>
> [...]
>
> -Christoffer
>

-- 
Shannon