On 2017/2/15 11:18, Dou Liyang wrote:
ccing Hanjun
Thank you for adding me in the loop.
At 02/15/2017 10:53 AM, Dou Liyang wrote:
Dear, Rafael
At 02/14/2017 06:18 AM, Rafael J. Wysocki wrote:
On Mon, Feb 13, 2017 at 2:31 PM, Dou Liyang
<douly.fnst@xxxxxxxxxxxxxx> wrote:
Hi, Rafael, Lv
May I ask for your help.
Recently, I am very confused about the generation of the MADT
in ACPI table.
1: Why we put all the Apic Ids which flag==1 in front of the
one which flag==0 in MADT?
Just like that:
-----orginal----------|-------MADT-------
Apic Id | Enable Flag | Apic Id | Enable Flag
0x00 1 0x00 1
0x02 1 0x02 1
0x04 0 0x10 1
0x06 0 0x12 1
0x10 1 0x04 0
0x12 1 0x06 0
0x14 0 0x14 0
0x16 0 0x16 0
If the flag is the same, It will not change the order.
-----orginal----------|-------MADT---------
Apic Id | Enable Flag | Apic Id | Enable Flag
0x00 0 0x00 0
0x02 0 0x02 0
0x04 0 0x04 0
0x06 0 0x06 0
0x10 0 0x10 0
0x12 0 0x12 0
0x14 0 0x14 0
0x16 0 0x16 0
2: If the order rule can be changed ?
If it can be done, What should I do?
Are you asking about Local APIC IDs?
Yes, it is. Something about *Processor Local APIC Structure*.
In MADT, Their arrangement may be different between the usable
processors and unusable processors(Processor Enabled is 1 or 0
in MADT).
The rule of the arrangement seems like that it makes the usable
processors in front of the unusable processors, when we generate
the MADT at the booting time. And it seems do not care about the
arrangement of the unusable processors.
Unfortunately, the unusable processors will be used in CPU hotplug.
And we also make the cpu_id <-> apic_id fixed according to the MADT
after linux-4.9. So the arrangement may be influence on the value of
CPUIds.
Can you specify the issues? maybe the logical CPU IDs are not
continuous in a numa node even two CPUs are hyper-threadings
in one core?
I am investigating this. So I hope to know:
1. How the MADT is generated, Where can I find the Method/Function of
the generation?
It depends on the firmware I think and lots of them are not open source,
you may try the UEFI tianocore project (www.tianocore.org).
2. Is there a rule used for the order of the Local APIC/x2APIC IDs?
I think not, there is no rules in the ACPI spec for the ordering
of processor entries (local apic/x2apic/gicc).
Thanks
Hanjun
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