Machines don't start with multiple CPUs (Gentoo compiler flags)

[dE]

I've a Windows VM, A live CD (system rescue CD), and another Sabayon Live distro all of which fail to boot if I've multiple CPUs enabled.

Virtualization is enabled with nested paging (on i3 2120) and i/o ACPI is enabled.

The bootloader loads, but once I've selected the OS to start (or kernel to load), all I see is a black screen. On system rescue CD, after the loading of the kernel and initramfs, once the kernel executes, nothing happens, just the previous text is shown (loading vmlinuz*, initramfs).

[Frank Mehnert]

What happens if you try to boot your guest with 2 guest CPUs?

[dE]

You cant close the bug. Strange.

The vanilla and official build of Virtualbox works. The Gentoo build is having issues.

[Frank Mehnert]

Any change with VBox 4.1.20? This might be a difference between the official build and builds made from the externally available source (the former OSE release) which shouldn't happen. Your guest does not use EFI to boot, does it?

[dE]

It has to do with Graphite (GCC). If Virtualbox (not modules) is compiled with -fomit-frame-pointer -floop-interchange -floop-strip-mine -floop-block -fgraphite-identity, it starts giving problems with multiple CPUs.

[Frank Mehnert]

Thanks for the investigation! In that case I will close this ticket as invalid. The VirtualBox compiler flags must not be changed. Using -fomit-frame-pointer changes the stack layout which does not work for some code.