Fix requested for SEV live-migration

[Khaled El Mously]

The following upstream fix is requested to resolve issues with SEV live-migration:

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=ac3f9c9f1b37edaa7d1a9b908bc79d843955a1a2

More details in:

https://canonical.lightning.force.com/lightning/r/Case/5008e00000HNdQ8AAL/view

Testing:
 - Boot-tested each of f/gcp, j/gcp and l/gcp
 - GCP has tested each of them as well and reported that the live-migration issue under SEV gets resolved.

Regression potential:
 - The change affects arch/x86/kernel/kvm.c so KVM on x86 can be impacted. It is a minimalistic change though, and regression risk is considered low.

[John Cabaj (john-cabaj)]

Fix was tested by Google, and the relevant patch is in all releases of linux-gcp affected.

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

This bug is awaiting verification that the linux-gcp-tcpx/5.15.0-1002.2 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-focal-linux-gcp-tcpx' to 'verification-done-focal-linux-gcp-tcpx'. If the problem still exists, change the tag 'verification-needed-focal-linux-gcp-tcpx' to 'verification-failed-focal-linux-gcp-tcpx'.

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!