Re: MP tables do not report multiple CPUs in Qemu 6.2.0 on x86 when given -smp cpus=n flag

[Godmar Back]

Thank you for the replies. I will note that I suspected SeaBIOS as
well. However, testing 6.2.0 with SeaBIOS 14 (which is the version
that shipped with 6.1.1) did not change the behavior, so I concluded
it was a change in Qemu, despite the fact that SeaBIOS is setting up
the tables.

I was about to write a note that this information is hard to find, but
I feel I need to apologize. When I go to the user manual [1] it
explains the change in behavior:

"Historically preference was given to the coarsest topology parameters
when computing missing values (ie sockets preferred over cores, which
were preferred over threads), however, this behaviour is considered
liable to change. Prior to 6.2 the preference was sockets over cores
over threads. Since 6.2 the preference is cores over sockets over
threads.

For example, the following option defines a machine board with 2
sockets of 1 core before 6.2 and 1 socket of 2 cores after 6.2:

-smp 2"

I should have checked first.

[1] https://www.qemu.org/docs/master/system/invocation.html