Patch submitted: https://lists.ubuntu.com/archives/kernel-
team/2025-September/162660.html

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https://bugs.launchpad.net/bugs/2121873

Title:
  Support TDX host in questing

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Questing:
  In Progress

Bug description:
  Since 6.16, TDX host is supported in the kernel but is incompatible with 
kexec.
  A cache flush is required in case TDX has been enabled before doing a kexec 
to avoid silent memory corruption in the new kernel.

  An upstream submission [0] fix this. The upstream submission is now a v8 and 
is likely to be merged soon.
  4 conditions are required at runtime to enable TDX Host:
  - Hibernation disabled.
  - TDX enabled in the bios.
  - kvm_intel.tdx=1 set in the bootcommand line.
  - Hardware support.

  Two limitation are coming with this submission:
  - In specific platforms (SPR/EMR), enabling TDX (all conditions fulfilled) 
will disable kexec due to hardware limitations.
  - After kexec, TDX can't be used. This error will manifest by having a dmesg 
entry similar to:

  virt/tdx: SEAMCALL (0x0000000000000021) failed: 0xc000050000000000


  This has been applied on top of questing Ubuntu-6.17.0-3.3 and tested
  on supported hardware by enabling TDX and using kexec into a new
  kernel.

  [0] :
  https://lore.kernel.org/all/[email protected]/

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