KVM: SEV: Decouple the need to sync the GHCB SA from the need to free the SA

KVM: SEV: Decouple the need to sync the GHCB SA from the need to free the SA

Decouple synchronizing the GHCB SA from freeing/unpinning the SA, so that
the free/unpin path can be reused when freeing a vCPU.

Opportunistically add a WARN to harden KVM against stomping over (and thus
leaking) an already-allocated scratch area.

Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-17-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20260529183549.1104619-17-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>