[SeaBIOS] [PATCH 1/2] fw/acpi: Build MADT the way commodity BIOSes do

[Sironi, Filippo]

> On 27 Jan 2017, at 06:27, Kevin O'Connor <kevin at koconnor.net> wrote:
> 
> On Fri, Jan 27, 2017 at 02:18:39AM +0100, Filippo Sironi wrote:
>> When running Linux on an Intel machine with a commodity BIOS, CPUs are
>> numbered starting from 0 and the first half refers to the first logical
>> CPU on each core while the second half refers to the second logical CPU
>> on each core.
>> As an example, on machine with 2 sockets, 4 cores per socket, and 2
>> logical CPUs per core, CPUs would be numbered:
>> 
>> *  0  1  2  3 - first logical CPU on each core of socket 0
>> *  4  5  6  7 - first logical CPU on each core of socket 1
>> *  8  9 10 11 - second logical CPU on each core of socket 0
>> * 12 13 14 15 - second logical CPU on each core of socket 1
>> 
>> With seabios (prior to this patch), CPU 0 would be the first logical CPU
>> on core 0 of socket 0, CPU 1 would be the second logical CPU on core 0
>> of socket 0, and so on.
>> This is due to the fact that processor_id and local_apic_id are assigned
>> with the same value when building MADT.
>> 
>> Exhaust the most-significant 7 bits of the 8-bit APIC ID and then come
>> back to the least-significant bit when assigning local_apic_id, since
>> the least-significant bit identifies the second logical CPU on a core.
>> 
>> If HTT isn't available, keep the previous behavior.
>> 
>> Signed-off-by: Filippo Sironi <sironi at amazon.de>
>> ---
>> src/fw/acpi.c | 42 +++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 41 insertions(+), 1 deletion(-)
>> 
>> diff --git a/src/fw/acpi.c b/src/fw/acpi.c
>> index 8bc2ca6..864c247 100644
>> --- a/src/fw/acpi.c
>> +++ b/src/fw/acpi.c
> 
> The acpi.c code in seabios is deprecated.  With all recent version of
> qemu/kvm the acpi tables are obtained from qemu.  So, if there is a
> desired change to the tables then a patch should be made for qemu.
> 
> -Kevin

What if someone is using SeaBIOS but isn't using QEMU?

Filippo


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