Address performance issue w/ GICv4-based guests

[dann frazier]

[Impact]
Performance is degraded when a guest is booted w/ vgic v4 support enabled.

[Test Case]
I used a HiSilicon D06 system w/ an Intel 82599 10Gbps NIC. I passed through a VF to a guest, and ran "netperf -H <host>" against a 10Gbps-capable target. With vgic v4 support, I'm only seeing 5-6Gbps. With vgic v3 support, this was in the 9Gbps spectrum. And, after applying the upstream fix, I'm also seeing >9Gbps w/ vgic v4 enabled.

Note: to enable vgic v4 support, pass "kvm-arm.vgic_v4_enable=1" on the host kernel cmdline.

[Fix]
ca71228b42a96 arm64: KVM: Always set ICH_HCR_EL2.EN if GICv4 is enabled

[Regression Risk]
The fix is restricted to the ARM/KVM subsystem.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1829942

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Kleber Sacilotto de Souza (kleber-souza)]

This patch has already been applied to Disco as part of the update to 5.0.12 upstream stable release (LP: #1830934).

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-cosmic' to 'verification-done-cosmic'. If the problem still exists, change the tag 'verification-needed-cosmic' to 'verification-failed-cosmic'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[dann frazier (dannf)]

Verified. From within a guest:

$ netperf -H <IP>
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to <IP> () port 0 AF_INET : demo
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec

131072 16384 16384 10.02 941.41

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Terry Rudd (terrykrudd)]

Dann, is this still planned for Eoan?

[dann frazier (dannf)]

On Wed, Aug 14, 2019 at 1:25 PM Terry Rudd <email address hidden> wrote:
>
> Dann, is this still planned for Eoan?

 This change is upstream in v5.1.

[Kleber Sacilotto de Souza (kleber-souza)]

This fix has already been released with disco linux 5.0.0-21.22, as part of the update to 5.0.12 upstream stable release (LP: #1830934). Therefore I'm marking it as 'Fix Released'.