[RFC PATCH v2 3/3] KVM: arm64: Add KVM_REQ_RELOAD_STAGE2

[Leonardo Bras <leo.bras@arm.com>]

Add a vcpu request to exit guest, reload Stage2, and then come back to
guest.

This will be used on future patches that enable HDBSS, as they may need to
change VTCR bits for enabling/disabling the feature when the vcpus are
still running.

On non-VHE systems, just skip this request as Stage2 is being reloaded
on every guest entry.

Signed-off-by: Leonardo Bras <leo.bras@arm.com>
---
 arch/arm64/include/asm/kvm_host.h |  2 ++
 arch/arm64/kvm/arm.c              | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index cd9b9d2462f9..86a4d6e50934 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -53,10 +53,12 @@
 #define KVM_REQ_RESYNC_PMU_EL0		KVM_ARCH_REQ(7)
 #define KVM_REQ_NESTED_S2_UNMAP		KVM_ARCH_REQ(8)
 #define KVM_REQ_GUEST_HYP_IRQ_PENDING	KVM_ARCH_REQ(9)
 #define KVM_REQ_MAP_L1_VNCR_EL2		KVM_ARCH_REQ(10)
 #define KVM_REQ_VGIC_PROCESS_UPDATE	KVM_ARCH_REQ(11)
+#define KVM_REQ_RELOAD_STAGE2 \
+	KVM_ARCH_REQ_FLAGS(12, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 
 #define KVM_DIRTY_LOG_MANUAL_CAPS   (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \
 				     KVM_DIRTY_LOG_INITIALLY_SET)
 
 #define KVM_HAVE_MMU_RWLOCK
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 0576c2022ef5..d311637e0b13 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1173,10 +1173,20 @@ static int check_vcpu_requests(struct kvm_vcpu *vcpu)
 			return kvm_vcpu_suspend(vcpu);
 
 		if (kvm_dirty_ring_check_request(vcpu))
 			return 0;
 
+		/* Non-vhe systems already reload Stage2 on guest entry */
+		if (kvm_check_request(KVM_REQ_RELOAD_STAGE2, vcpu) &&
+		    has_vhe()) {
+			unsigned long flags;
+
+			local_irq_save(flags);
+			__load_stage2(vcpu->arch.hw_mmu);
+			local_irq_restore(flags);
+		}
+
 		check_nested_vcpu_requests(vcpu);
 	}
 
 	return 1;
 }
-- 
2.56.0