KVM: arm64: Convert vcpu sysregs_loaded_on_cpu to a state flag

The aptly named boolean 'sysregs_loaded_on_cpu' tracks whether
some of the vcpu system registers are resident on the physical
CPU when running in VHE mode.

This is obviously a flag in hidding, so let's convert it to
a state flag, since this is solely a host concern (the hypervisor
itself always knows which state we're in).
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/include/asm/kvm_host.h

@@ -410,10 +410,6 @@ struct kvm_vcpu_arch {
 	/* Additional reset state */
 	struct vcpu_reset_state	reset_state;
 
-	/* True when deferrable sysregs are loaded on the physical CPU,
-	 * see kvm_vcpu_load_sysregs_vhe and kvm_vcpu_put_sysregs_vhe. */
-	bool sysregs_loaded_on_cpu;
-
 	/* Guest PV state */
 	struct {
 		u64 last_steal;
@@ -520,6 +516,8 @@ struct kvm_vcpu_arch {
 #define ON_UNSUPPORTED_CPU	__vcpu_single_flag(sflags, BIT(2))
 /* WFIT instruction trapped */
 #define IN_WFIT			__vcpu_single_flag(sflags, BIT(3))
+/* vcpu system registers loaded on physical CPU */
+#define SYSREGS_ON_CPU		__vcpu_single_flag(sflags, BIT(4))
 
 /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
 #define vcpu_sve_pffr(vcpu) (kern_hyp_va((vcpu)->arch.sve_state) +	\

arch/arm64/kvm/hyp/vhe/sysreg-sr.c

@@ -79,7 +79,7 @@ void kvm_vcpu_load_sysregs_vhe(struct kvm_vcpu *vcpu)
 	__sysreg_restore_user_state(guest_ctxt);
 	__sysreg_restore_el1_state(guest_ctxt);
 
-	vcpu->arch.sysregs_loaded_on_cpu = true;
+	vcpu_set_flag(vcpu, SYSREGS_ON_CPU);
 
 	activate_traps_vhe_load(vcpu);
 }
@@ -110,5 +110,5 @@ void kvm_vcpu_put_sysregs_vhe(struct kvm_vcpu *vcpu)
 	/* Restore host user state */
 	__sysreg_restore_user_state(host_ctxt);
 
-	vcpu->arch.sysregs_loaded_on_cpu = false;
+	vcpu_clear_flag(vcpu, SYSREGS_ON_CPU);
 }

arch/arm64/kvm/sys_regs.c

@@ -72,7 +72,7 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
 {
 	u64 val = 0x8badf00d8badf00d;
 
-	if (vcpu->arch.sysregs_loaded_on_cpu &&
+	if (vcpu_get_flag(vcpu, SYSREGS_ON_CPU) &&
 	    __vcpu_read_sys_reg_from_cpu(reg, &val))
 		return val;
 
@@ -81,7 +81,7 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
 
 void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
 {
-	if (vcpu->arch.sysregs_loaded_on_cpu &&
+	if (vcpu_get_flag(vcpu, SYSREGS_ON_CPU) &&
 	    __vcpu_write_sys_reg_to_cpu(val, reg))
 		return;