[BitVisor-devel-en:87] Re: UEFI Multicore?

[Hideki EIRAKU]

Hello,

From: "Dr. Lonnie Cumberland, PhD" <lonnie at outstep.com>
Subject: [BitVisor-devel-en:86] UEFI Multicore?
Date: Thu, 25 Jan 2024 18:51:52 -0500

> In my reading about uefi applications, the information seems to
> suggest that there is not any real type of threading in the normal
> sense that we use it in programming, but that the uefi application
> typically uses only a single "core" for the application.  Upon further
> reading, it also seems that you can start up and use other cores as
> well which made me wonder if bitvisor is all run on a single core in a
> single thread?

BitVisor acts about multicore passively.  Especially on UEFI
environment, the multicore is not started until the guest operating
system starts them.  This is because I saw a machine that does not
work properly at ExitBootServices if multicore was started by BitVisor
- I thought the firmware expects something special code running on the
core.

BitVisor monitors the guest I/O or some instructions and do something
in hypervisor, but does not control about multicores (like moving to
different cores or taking control of a core), so the guest sees real
cores as is - i.e. the core 0 thread 0 in the guest is always really
on core 0 thread 0 on the host machine.  If the CPU0 does I/O which is
intercepted by BitVisor, BitVisor handles the I/O in CPU0.

-- 
Hideki EIRAKU <hdk at igel.co.jp>