KVM: arm64: Trap host SMCs in protected mode

While protected KVM is installed, start trapping all host SMCs.
For now these are simply forwarded to EL3, except PSCI
CPU_ON/CPU_SUSPEND/SYSTEM_SUSPEND which are intercepted and the
hypervisor installed on newly booted cores.

Create new constant HCR_HOST_NVHE_PROTECTED_FLAGS with the new set of HCR
flags to use while the nVHE vector is installed when the kernel was
booted with the protected flag enabled. Switch back to the default HCR
flags when switching back to the stub vector.
Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201202184122.26046-26-dbrazdil@google.com

arch/arm64/include/asm/kvm_arm.h

@@ -80,6 +80,7 @@
 			 HCR_FMO | HCR_IMO | HCR_PTW )
 #define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF)
 #define HCR_HOST_NVHE_FLAGS (HCR_RW | HCR_API | HCR_APK | HCR_ATA)
+#define HCR_HOST_NVHE_PROTECTED_FLAGS (HCR_HOST_NVHE_FLAGS | HCR_TSC)
 #define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)
 
 /* TCR_EL2 Registers bits */

arch/arm64/kvm/hyp/nvhe/hyp-init.S

@@ -88,6 +88,11 @@ SYM_CODE_END(__kvm_hyp_init)
  * x0: struct kvm_nvhe_init_params PA
  */
 SYM_CODE_START_LOCAL(___kvm_hyp_init)
+alternative_if ARM64_KVM_PROTECTED_MODE
+	mov_q	x1, HCR_HOST_NVHE_PROTECTED_FLAGS
+	msr	hcr_el2, x1
+alternative_else_nop_endif
+
 	ldr	x1, [x0, #NVHE_INIT_TPIDR_EL2]
 	msr	tpidr_el2, x1
 
@@ -230,6 +235,11 @@ reset:
 	msr	sctlr_el2, x5
 	isb
 
+alternative_if ARM64_KVM_PROTECTED_MODE
+	mov_q	x5, HCR_HOST_NVHE_FLAGS
+	msr	hcr_el2, x5
+alternative_else_nop_endif
+
 	/* Install stub vectors */
 	adr_l	x5, __hyp_stub_vectors
 	msr	vbar_el2, x5

arch/arm64/kvm/hyp/nvhe/switch.c

@@ -96,6 +96,9 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu)
 	mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;
 
 	write_sysreg(mdcr_el2, mdcr_el2);
+	if (is_protected_kvm_enabled())
+		write_sysreg(HCR_HOST_NVHE_PROTECTED_FLAGS, hcr_el2);
+	else
 		write_sysreg(HCR_HOST_NVHE_FLAGS, hcr_el2);
 	write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
 	write_sysreg(__kvm_hyp_host_vector, vbar_el2);