topic Re: Strage crashing using virtualization on 32bit guests with i7-10700 in Mobile and Desktop Processors

Strage crashing using virtualization on 32bit guests with i7-10700

laffer1 — Thu, 13 Aug 2020 13:47:41 GMT

I just upgraded a system from a i7-7700 to a i7-10700. The hardware is nearly identical except for the CPU and motherboard. It's an asrock z490m.

The host operating system is vmware esxi 7.0b. (originally 7.0, but i tried upgrading)

When a 64bit guest is used, the system seems to work fine. A 32bit guest running MidnightBSD can cause a double fault when running certain applications. I've got a 100% reproducible case but I haven't been able to narrow it down to the exact command yet. It's a shell script (bsdstats) running several programs. I also have seen it when compiling part of QT5.

I'm not sure it's actually a bug with the CPU or UEFI, but the same code does work on a i7-7700.

Things I've tried:
* updating the bios to the latest.

* Turning SR-IOV on/off, and sxguard settings

* Slowing down the RAM to DDR4 2133 rather than 2933. They're corsair modules.

* Enabling a DEBUG kernel in the operating system. Seems to only capture the second fault as far as i can tell.

As it's a 10700 (not a k or f variant), it's not overclocked. It's using the stock cooler. It's a pretty boring setup. The onboard NIC wasn't supported in vmware so i put in an older intel pro gigabit nic. The memory modules are listed as supported but not overclockable on the asrock site. There are 4 8GB modules.

The guest system has 3GB of RAM allocated and 8 virtual cores.

Has anyone else experienced any issues with 32bit guests on these processors?

Re: Strage crashing using virtualization on 32bit guests with i7-10700

laffer1 — Thu, 13 Aug 2020 19:15:37 GMT

I've narrowed it down to /bin/mksh. Anytime that runs, it crashes. It does not happen on FreeBSD i386 10.4 running in a VM. I've also tried GCC instead of LLVM to build mksh and it still happens. I've tried a newer mksh and it happens.

I'm wondering if it's some kind of alignment issue and the newer CPU is just pickier about it.

I also tried an older MidnightBSD release (1.1) and it will launch mksh, but still crashes when mksh runs the bsdstats script in the same way.

Re: Strage crashing using virtualization on 32bit guests with i7-10700

laffer1 — Sat, 15 Aug 2020 03:57:15 GMT

I can't explain why it works on the older i7-7700 and not the i7-10700, but it seems to be OS specific and was worked around with an increase in the kernel stack size. For some reason, the stack used is larger on the newer CPU.