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[Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows
From: |
Dr. David Alan Gilbert |
Subject: |
[Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection |
Date: |
Tue, 18 Sep 2018 10:49:39 -0000 |
I don't think we should see a vmexit on a guest user<->kernel switch.
You could try a kvm trace:
trace-cmd record -b 20000 -e kvm
run your test, then ctrl-c
then
trace-cmd report
and you can see all the reasons for exit and see if there are any major
differences.
Yes, it would be good to know if it happened under other hypervisors;
although this one is tricky since it's Windows guest with nvidia closed
drivers, so it's a bit tricky to know what's going on.
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https://bugs.launchpad.net/bugs/1788665
Title:
Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM
using "Spectre" protection
Status in QEMU:
New
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
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- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/09/05
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Dr. David Alan Gilbert, 2018/09/05
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/11
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/14
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Dr. David Alan Gilbert, 2018/09/14
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/14
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/17
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection,
Dr. David Alan Gilbert <=
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/18
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/18
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Dr. David Alan Gilbert, 2018/09/19
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/19
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, George Amanakis, 2018/09/19
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Dr. David Alan Gilbert, 2018/09/19