|On 15 Nov 2018, at 06:59, A Z <adam zegelin com> wrote:|
This sounds quite like a problem I used to have in the past with certain versions of OVMF and the Linux kernel. If I remember correctly, some memory ranges would get marked as non-cacheable, which resulted in the terrible slowdown you describe. The resolution back then was to stick to older versions of both the firmware and the kernel.
I still keep around an older version of OVMF that I used until recently - edk2.git-ovmf-x64-0-20160714.b1992.gfc3005.noarch.rpm. You could download the RPM here and try if it works for you:
Recent QEMU versions started complaining about firmware incompatibilities, so I tried the latest RPM from Kraxel (https://www.kraxel.org/repos/jenkins/edk2/) and it works just fine. The host system is Arch Linux with the latest Arch kernel and QEMU.