hyperv: SVM enlightened TLB flush support flag

Bit 22 of HYPERV_CPUID_FEATURES.EDX is specific to SVM and specifies
support for enlightened TLB flush. With this enlightenment enabled,
ASID invalidations flushes only gva->hpa entries. To flush TLB entries
derived from NPT, hypercalls should be used
(HvFlushGuestPhysicalAddressSpace or HvFlushGuestPhysicalAddressList)

Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Message-Id: <a060f872d0df1955e52e30b877b3300485edb27c.1622730232.git.viremana@linux.microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/hyperv-tlfs.h

@@ -138,6 +138,15 @@
 #define HV_X64_NESTED_GUEST_MAPPING_FLUSH		BIT(18)
 #define HV_X64_NESTED_MSR_BITMAP			BIT(19)
 
+/*
+ * This is specific to AMD and specifies that enlightened TLB flush is
+ * supported. If guest opts in to this feature, ASID invalidations only
+ * flushes gva -> hpa mapping entries. To flush the TLB entries derived
+ * from NPT, hypercalls should be used (HvFlushGuestPhysicalAddressSpace
+ * or HvFlushGuestPhysicalAddressList).
+ */
+#define HV_X64_NESTED_ENLIGHTENED_TLB			BIT(22)
+
 /* HYPERV_CPUID_ISOLATION_CONFIG.EAX bits. */
 #define HV_PARAVISOR_PRESENT				BIT(0)