Public bug reported:

[Impact]
On dual GFX systems, if amdgpu fails to probe a device, vgaarb for
another GFX triggers a NULL pointer dereference and freeze the system.

[Fix]
Defer VGA client registering so resources are handled properly when
amdgpu probe fails.
        
[Test]          
With the patch applied, no more kernel panic when vgaarb is changing the
VGA mode.
        
[Where problems could occur]
VGA clients won't take effect until a successful probe, so unless there
is very subtle bug in vgaarb or vgaswitcheroo, it's very unlikely to
introduce any regression.

** Affects: hwe-next
     Importance: Undecided
         Status: New

** Affects: linux (Ubuntu)
     Importance: Critical
         Status: Confirmed

** Affects: linux-oem-5.10 (Ubuntu)
     Importance: Undecided
         Status: Invalid

** Affects: linux (Ubuntu Focal)
     Importance: Undecided
         Status: Won't Fix

** Affects: linux-oem-5.10 (Ubuntu Focal)
     Importance: Critical
         Status: Confirmed

** Affects: linux (Ubuntu Hirsute)
     Importance: Critical
         Status: Confirmed

** Affects: linux-oem-5.10 (Ubuntu Hirsute)
     Importance: Undecided
         Status: Invalid


** Tags: oem-priority originate-from-1914566 stella

** Also affects: linux-oem-5.10 (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: linux (Ubuntu Focal)
   Importance: Undecided
       Status: New

** Also affects: linux-oem-5.10 (Ubuntu Focal)
   Importance: Undecided
       Status: New

** Also affects: linux (Ubuntu Hirsute)
   Importance: Undecided
       Status: New

** Also affects: linux-oem-5.10 (Ubuntu Hirsute)
   Importance: Undecided
       Status: New

** Changed in: linux-oem-5.10 (Ubuntu Hirsute)
       Status: New => Invalid

** Changed in: linux-oem-5.10 (Ubuntu)
       Status: New => Invalid

** Changed in: linux (Ubuntu Focal)
       Status: New => Won't Fix

** Changed in: linux (Ubuntu)
       Status: New => Confirmed

** Changed in: linux (Ubuntu Hirsute)
       Status: New => Confirmed

** Changed in: linux-oem-5.10 (Ubuntu Focal)
       Status: New => Confirmed

** Changed in: linux (Ubuntu)
   Importance: Undecided => Critical

** Changed in: linux (Ubuntu Hirsute)
   Importance: Undecided => Critical

** Changed in: linux-oem-5.10 (Ubuntu Focal)
   Importance: Undecided => Critical

** Tags added: oem-priority originate-from-1914566 stella

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https://bugs.launchpad.net/bugs/1926792

Title:
  Fix kernel panic at boot on dual GFX systems

Status in HWE Next:
  New
Status in linux package in Ubuntu:
  Confirmed
Status in linux-oem-5.10 package in Ubuntu:
  Invalid
Status in linux source package in Focal:
  Won't Fix
Status in linux-oem-5.10 source package in Focal:
  Confirmed
Status in linux source package in Hirsute:
  Confirmed
Status in linux-oem-5.10 source package in Hirsute:
  Invalid

Bug description:
  [Impact]
  On dual GFX systems, if amdgpu fails to probe a device, vgaarb for
  another GFX triggers a NULL pointer dereference and freeze the system.

  [Fix]
  Defer VGA client registering so resources are handled properly when
  amdgpu probe fails.
          
  [Test]          
  With the patch applied, no more kernel panic when vgaarb is changing the
  VGA mode.
          
  [Where problems could occur]
  VGA clients won't take effect until a successful probe, so unless there
  is very subtle bug in vgaarb or vgaswitcheroo, it's very unlikely to
  introduce any regression.

To manage notifications about this bug go to:
https://bugs.launchpad.net/hwe-next/+bug/1926792/+subscriptions

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