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

[Kevin O'Connor]

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