[REGRESSION] [6.12.y] crypto: ccp - Move SEV/SNP Platform initialization to KVM breaks SEV-ES VM launch

[Andrew Wilson]

#regzbot introduced: 3f8f0133a5fc9b32d0c308530320c3f2430ba5ab

Hi all,

I am writing to report a regression affecting AMD SEV-ES VM launches
on the 6.12 stable branch (first noticed in 6.12.97+ / 6.12.101).

I completed a git bisect between working and failing kernels, which pointed to:

Commit: bb1c84647025 ("crypto: ccp - Move SEV/SNP Platform
initialization to KVM")
Upstream commit: 3f8f0133a5fc9b32d0c308530320c3f2430ba5ab

### Bisect & Verification Details:
* Last Known Working: 8a599f4f74d4
* First Broken Commit: bb1c84647025
* Tested on 6.12.101: Cleanly reverting bb1c84647025 immediately
resolves the issue and allows SEV-ES guests to boot normally.

### Failure Description:
With commit bb1c84647025 applied, `sev_platform_init(&args)` is
removed from `sev_pci_init()`, assuming KVM handles on-demand
initialization.

On bare metal, the PSP firmware appears to remain uninitialized (does
not reach SEV_STATE_INIT at probe time). When QEMU initializes KVM and
queries host SEV-ES capabilities, the ioctl fails with -EPERM:

  qemu-system-x86_64: -accel kvm: sev_common_kvm_init: guest policy
requires SEV-ES, but host SEV-ES support unavailable
  qemu-system-x86_64: -accel kvm: failed to initialize kvm: Operation
not permitted

### Hardware & Environment:
* Tested on: AMD EPYC (Rome / Milan) Supermicro platforms
* Kernel: Linux 6.12.101
* Hypervisor: QEMU / KVM

I have access to Naples, Rome, and Milan test hardware and am happy to
test any patches, provide dmesg traces, or assist with debugging.  I
am not a tech-expert of any kind, but I have time to do some testing
if it helps.  THANK YOU for the great work.

Original Debian bug reference:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1145026

Thanks,
Andrew Wilson