[Bug 2121873] Re: Support TDX host in questing

** Changed in: linux (Ubuntu Questing)
Status: In Progress => Fix Committed

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

Title:
Support TDX host in questing

Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Questing:
Fix Committed

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/20250901160930.1785244-1-pbonzini@redhat.com/

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