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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: |
Fri, 31 Aug 2018 09:45:38 -0000 |
I find it interesting this is a slow down with PCI passthrough - that's
pretty much the case you'd expect there to be least change; it shouldn't
be generating lots of vm exit's for example which you'd expect could
have been made slower by the recent security changes.
I suppose one thing you could try is profiling on the host to see if
more time is spent in the host kernel or qemu when running the 2d tests
with the new vs older windows; if it points to some particular hot spot
there then perhaps it might be possible to understand why.
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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, (continued)
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/08/25
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/08/25
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Daniel Berrange, 2018/08/28
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/08/28
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/08/30
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/08/30
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Daniel Berrange, 2018/08/30
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/08/30
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Daniel Berrange, 2018/08/30
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection, Heiko Sieger, 2018/08/30
- [Qemu-devel] [Bug 1788665] Re: Low 2D graphics performance with Windows 10 (1803) VGA passthrough VM using "Spectre" protection,
Dr. David Alan Gilbert <=