KVM: x86: Define more SEV+ page fault error bits/flags for #NPF

Define more #NPF error code flags that are relevant to SEV+ (mostly SNP)
guests, as specified by the APM:

 * Bit 31 (RMP):   Set to 1 if the fault was caused due to an RMP check or a
                   VMPL check failure, 0 otherwise.
 * Bit 34 (ENC):   Set to 1 if the guest’s effective C-bit was 1, 0 otherwise.
 * Bit 35 (SIZEM): Set to 1 if the fault was caused by a size mismatch between
                   PVALIDATE or RMPADJUST and the RMP, 0 otherwise.
 * Bit 36 (VMPL):  Set to 1 if the fault was caused by a VMPL permission
                   check failure, 0 otherwise.

Note, the APM is *extremely* misleading, and strongly implies that the
above flags can _only_ be set for #NPF exits from SNP guests.  That is a
lie, as bit 34 (C-bit=1, i.e. was encrypted) can be set when running _any_
flavor of SEV guest on SNP capable hardware.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240228024147.41573-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -261,8 +261,12 @@ enum x86_intercept_stage;
 #define PFERR_FETCH_MASK	BIT(4)
 #define PFERR_PK_MASK		BIT(5)
 #define PFERR_SGX_MASK		BIT(15)
+#define PFERR_GUEST_RMP_MASK	BIT_ULL(31)
 #define PFERR_GUEST_FINAL_MASK	BIT_ULL(32)
 #define PFERR_GUEST_PAGE_MASK	BIT_ULL(33)
+#define PFERR_GUEST_ENC_MASK	BIT_ULL(34)
+#define PFERR_GUEST_SIZEM_MASK	BIT_ULL(35)
+#define PFERR_GUEST_VMPL_MASK	BIT_ULL(36)
 #define PFERR_IMPLICIT_ACCESS	BIT_ULL(48)
 
 #define PFERR_NESTED_GUEST_PAGE (PFERR_GUEST_PAGE_MASK |	\