KVM: arm64: Save PSTATE early on exit

In order to be able to use primitives such as vcpu_mode_is_32bit(),
we need to synchronize the guest PSTATE. However, this is currently
done deep into the bowels of the world-switch code, and we do have
helpers evaluating this much earlier (__vgic_v3_perform_cpuif_access
and handle_aarch32_guest, for example).

Move the saving of the guest pstate into the early fixups, which
cures the first issue. The second one will be addressed separately.
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -429,6 +429,12 @@ static inline bool kvm_hyp_handle_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
  */
 static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 {
+	/*
+	 * Save PSTATE early so that we can evaluate the vcpu mode
+	 * early on.
+	 */
+	vcpu->arch.ctxt.regs.pstate = read_sysreg_el2(SYS_SPSR);
+
 	if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ)
 		vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR);
 

arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h

@@ -70,7 +70,12 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 static inline void __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt)
 {
 	ctxt->regs.pc			= read_sysreg_el2(SYS_ELR);
-	ctxt->regs.pstate		= read_sysreg_el2(SYS_SPSR);
+	/*
+	 * Guest PSTATE gets saved at guest fixup time in all
+	 * cases. We still need to handle the nVHE host side here.
+	 */
+	if (!has_vhe() && ctxt->__hyp_running_vcpu)
+		ctxt->regs.pstate	= read_sysreg_el2(SYS_SPSR);
 
 	if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN))
 		ctxt_sys_reg(ctxt, DISR_EL1) = read_sysreg_s(SYS_VDISR_EL2);