KVM: arm64: Add a vcpu flag to control SVE visibility for the guest

Since SVE will be enabled or disabled on a per-vcpu basis, a flag
is needed in order to track which vcpus have it enabled.

This patch adds a suitable flag and a helper for checking it.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/include/asm/kvm_host.h

@@ -328,6 +328,10 @@ struct kvm_vcpu_arch {
 #define KVM_ARM64_FP_HOST		(1 << 2) /* host FP regs loaded */
 #define KVM_ARM64_HOST_SVE_IN_USE	(1 << 3) /* backup for host TIF_SVE */
 #define KVM_ARM64_HOST_SVE_ENABLED	(1 << 4) /* SVE enabled for EL0 */
+#define KVM_ARM64_GUEST_HAS_SVE		(1 << 5) /* SVE exposed to guest */
+
+#define vcpu_has_sve(vcpu) (system_supports_sve() && \
+			    ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_SVE))
 
 #define vcpu_gp_regs(v)		(&(v)->arch.ctxt.gp_regs)