I've switched hosts so I would have to run a series of tests to compare. There are a number of new variables:
1. Windows 10 release (I'm now on Windows 2004) 2. My host OS is now Manjaro 3. CPU is now AMD Ryzen 3900X (before it was Intel 3930k) 4. Kernel is 5.8.18-1-MANJARO 5. qemu 5.1.0 6. libvirt 6.5.0 7. New VM configuration using virt-manager/libvirt with EPYC-IBPB model instead of host-passthrough, instead of a qemu bash script to launch the VM. Time permitting, I plan to replace Manjaro for a Ubuntu 20.04 based distro. But this will not happen in the very near future. In the meantime I will do some a/b tests with spectre protection under Windows enabled/disabled to see if it is still an issue. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1788665 Title: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection Status in QEMU: Incomplete Bug description: Windows 10 (1803) VM using VGA passthrough via qemu script. After upgrading Windows 10 Pro VM to version 1803, or possibly after applying the March/April security updates from Microsoft, the VM would show low 2D graphics performance (sluggishness in 2D applications and low Passmark results). Turning off Spectre vulnerability protection in Windows remedies the issue. Expected behavior: qemu/kvm hypervisor to expose firmware capabilities of host to guest OS - see https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/CVE-2017-5715-and-hyper-v-vms Background: Starting in March or April Microsoft began to push driver updates in their updates / security updates. See https://support.microsoft.com /en-us/help/4073757/protect-your-windows-devices-against-spectre- meltdown One update concerns the Intel microcode - see https://support.microsoft.com/en-us/help/4100347. It is activated by default within Windows. Once the updates are applied within the Windows guest, 2D graphics performance drops significantly. Other performance benchmarks are not affected. A bare metal Windows installation does not display a performance loss after the update. See https://heiko-sieger.info/low-2d-graphics- benchmark-with-windows-10-1803-kvm-vm/ Similar reports can be found here: https://www.reddit.com/r/VFIO/comments/97unx4/passmark_lousy_2d_graphics_performance_on_windows/ Hardware: 6 core Intel Core i7-3930K (-MT-MCP-) Host OS: Linux Mint 19/Ubuntu 18.04 Kernel: 4.15.0-32-generic x86_64 Qemu: QEMU emulator version 2.11.1 Intel microcode (host): 0x714 dmesg | grep microcode [ 0.000000] microcode: microcode updated early to revision 0x714, date = 2018-05-08 [ 2.810683] microcode: sig=0x206d7, pf=0x4, revision=0x714 [ 2.813340] microcode: Microcode Update Driver: v2.2. Note: I manually updated the Intel microcode on the host from 0x713 to 0x714. However, both microcode versions produce the same result in the Windows guest. Guest OS: Windows 10 Pro 64 bit, release 1803 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1788665/+subscriptions
