FPS of glxgear with fullscreen is too low on MTL platform

[AceLan Kao]

[Impact]
Run `glxgears -fullscreen` and the FPS can't stay at 60 FPS
298 frames in 5.0 seconds = 59.465 FPS
241 frames in 5.0 seconds = 48.193 FPS
261 frames in 5.0 seconds = 52.030 FPS
268 frames in 5.0 seconds = 53.596 FPS

[Fix]
Bisect the kernel and found a commit in v6.9-rc1 fixes the issue
c08c364102d0 drm/i915: Bypass LMEMBAR/GTTMMADR for MTL stolen memory access

[Test]
1. Run `glxgears -fullscreen` on MTL platforms
2. The FPS should be always around 60

[Where problems could occur]
It's a workaround only affects MTL platforms, and there is no "fixed commit" for this patch after v6.9-rc1. So, it should be safe and essential for MTL platforms.

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

This bug is awaiting verification that the linux-oem-6.8/6.8.0-1007.7 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-noble-linux-oem-6.8' to 'verification-done-noble-linux-oem-6.8'. If the problem still exists, change the tag 'verification-needed-noble-linux-oem-6.8' to 'verification-failed-noble-linux-oem-6.8'.

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!

[AceLan Kao (acelankao)]

Verified with 6.8.0-1007.7 kernel.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-oem-6.8 - 6.8.0-1007.7

---------------
linux-oem-6.8 (6.8.0-1007.7) noble; urgency=medium

  * noble/linux-oem-6.8: 6.8.0-1007.7 -proposed tracker (LP: #2068142)

  * Packaging resync (LP: #1786013)
    - [Packaging] Replace fs/cifs with fs/smb in inclusion list

  * Panels show garbage or flickering when i915.psr2 enabled (LP: #2069993)
    - SAUCE: drm/i915/display/psr: add a psr2 disable quirk table
    - SAUCE: drm/i915/display/psr: disable psr2 for panel_0x4d_0x10_0x93_0x15
    - SAUCE: drm/i915/display/psr: disable psr2 for panel_0x30_0xe4_0x8b_0x07
    - SAUCE: drm/i915/display/psr: disable psr2 for panel_0x30_0xe4_0x78_0x07
    - SAUCE: drm/i915/display/psr: disable psr2 for panel_0x30_0xe4_0x8c_0x07
    - SAUCE: drm/i915/display/psr: disable psr2 for panel_0x06_0xaf_0x9a_0xf9
    - SAUCE: drm/i915/display/psr: disable psr2 for panel_0x4d_0x10_0x8f_0x15
    - SAUCE: drm/i915/display/psr: disable psr2 for panel_0x06_0xaf_0xa3_0xc3

  * FPS of glxgear with fullscreen is too low on MTL platform (LP: #2069380)
    - drm/i915: Bypass LMEMBAR/GTTMMADR for MTL stolen memory access

  * amdgpu hangs on DCN 3.5 at bootup: RIP:
    0010:dcn35_clk_mgr_construct+0x183/0x2210 [amdgpu] (LP: #2066233)
    - drm/amd/display: Atom Integrated System Info v2_2 for DCN35

  [ Ubuntu: 6.8.0-36.36 ]

  * noble/linux: 6.8.0-36.36 -proposed tracker (LP: #2068150)
  * CVE-2024-26924
    - netfilter: nft_set_pipapo: do not free live element

  [ Ubuntu: 6.8.0-35.35 ]

  * noble/linux: 6.8.0-35.35 -proposed tracker (LP: #2065886)
  * CVE-2024-21823
    - VFIO: Add the SPR_DSA and SPR_IAX devices to the denylist
    - dmaengine: idxd: add a new security check to deal with a hardware erratum
    - dmaengine: idxd: add a write() method for applications to submit work

 -- Kuan-Ying Lee <email address hidden> Wed, 26 Jun 2024 14:17:06 +0800

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

This bug is awaiting verification that the linux/6.8.0-40.40 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-noble-linux' to 'verification-done-noble-linux'. If the problem still exists, change the tag 'verification-needed-noble-linux' to 'verification-failed-noble-linux'.

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!