KVM: x86: Prioritize CPUID faulting over CPUID VM-exits in nested VMX

KVM: x86: Prioritize CPUID faulting over CPUID VM-exits in nested VMX

Per the Intel SDM, "Certain exceptions have priority over VM exits.  These
include invalid-opcode exceptions, faults based on privilege level, and
general-protection exceptions that are based on checking I/O permission
bits in the task-state segment (TSS)."

Ensure that when L2 executes CPUID at CPL > 0 while L1 has enabled CPUID
faulting, KVM intercepts the exit in L0 and queues #GP rather than
forwarding the CPUID VM-exit to L1.

Empirical testing confirms that this #GP has higher precedence than a CPUID
VM-exit on Granite Rapids (F/M/S 6/0xad/1).

Fixes: db2336a80489 ("KVM: x86: virtualize cpuid faulting")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260513224608.1859737-1-jmattson%40google.com?part=3
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260527174347.2356165-3-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>