KVM: SVM: Inject #GP if memory operand for INVPCID is non-canonical

KVM: SVM: Inject #GP if memory operand for INVPCID is non-canonical

Inject a #GP if the memory operand received by INVCPID is non-canonical.
The APM clearly states that the intercept takes priority over all #GP
checks except the CPL0 restriction.

Of course, that begs the question of how the CPU generates a linear
address in the first place.  Tracing confirms that EXITINFO1 does hold a
linear address, at least for 64-bit mode guests (hooray GS prefix).
Unfortunately, the APM says absolutely nothing about the EXITINFO fields
for INVPCID intercepts, so it's not at all clear what's supposed to
happen.

Add a FIXME to call out that KVM still does the wrong thing for 32-bit
guests, and if the stack segment is used for the memory operand.

Cc: Babu Moger <babu.moger@amd.com>
Cc: Jim Mattson <jmattson@google.com>
Fixes: 4407a797e941 ("KVM: SVM: Enable INVPCID feature on AMD")
Link: https://lore.kernel.org/r/20250224174522.2363400-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>