From: Christoffer Dall <christoffer.dall@linaro.org>
Date: Tue, 10 Oct 2017 10:21:18 +0200
Subject: KVM: arm/arm64: Add kvm_vcpu_load_sysregs and kvm_vcpu_put_sysregs
Patch-mainline: v4.17-rc1
Git-commit: bc192ceec37108bf6c04a5c5795fcea5f940b0de
References: bsc#1085308 CVE-2018-3639

As we are about to move a bunch of save/restore logic for VHE kernels to
the load and put functions, we need some infrastructure to do this.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Liang Yan <lyan@suse.com>
---
 arch/arm/include/asm/kvm_host.h   |    3 +++
 arch/arm64/include/asm/kvm_host.h |    3 +++
 arch/arm64/kvm/hyp/sysreg-sr.c    |   30 ++++++++++++++++++++++++++++++
 virt/kvm/arm/arm.c                |    2 ++
 4 files changed, 38 insertions(+)

--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -319,4 +319,7 @@ static inline bool kvm_arm_harden_branch
 	return false;
 }
 
+static inline void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu) {}
+static inline void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu) {}
+
 #endif /* __ARM_KVM_HOST_H__ */
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -442,4 +442,7 @@ static inline bool kvm_arm_harden_branch
 	return cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR);
 }
 
+void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu);
+void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);
+
 #endif /* __ARM64_KVM_HOST_H__ */
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -190,6 +190,36 @@ void __hyp_text __sysreg32_restore_state
 		write_sysreg(sysreg[DBGVCR32_EL2], dbgvcr32_el2);
 }
 
+/**
+ * kvm_vcpu_load_sysregs - Load guest system registers to the physical CPU
+ *
+ * @vcpu: The VCPU pointer
+ *
+ * Load system registers that do not affect the host's execution, for
+ * example EL1 system registers on a VHE system where the host kernel
+ * runs at EL2.  This function is called from KVM's vcpu_load() function
+ * and loading system register state early avoids having to load them on
+ * every entry to the VM.
+ */
+void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu)
+{
+}
+
+/**
+ * kvm_vcpu_put_sysregs - Restore host system registers to the physical CPU
+ *
+ * @vcpu: The VCPU pointer
+ *
+ * Save guest system registers that do not affect the host's execution, for
+ * example EL1 system registers on a VHE system where the host kernel
+ * runs at EL2.  This function is called from KVM's vcpu_put() function
+ * and deferring saving system register state until we're no longer running the
+ * VCPU avoids having to save them on every exit from the VM.
+ */
+void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu)
+{
+}
+
 void __hyp_text __kvm_set_tpidr_el2(u64 tpidr_el2)
 {
 	asm("msr tpidr_el2, %0": : "r" (tpidr_el2));
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -359,10 +359,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu
 	kvm_arm_set_running_vcpu(vcpu);
 	kvm_vgic_load(vcpu);
 	kvm_timer_vcpu_load(vcpu);
+	kvm_vcpu_load_sysregs(vcpu);
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
+	kvm_vcpu_put_sysregs(vcpu);
 	kvm_timer_vcpu_put(vcpu);
 	kvm_vgic_put(vcpu);