[RFC PATCH v2 24/24] KVM: arm64: Use the shadow vCPU structure in handle___kvm_vcpu_run()

[Will Deacon]

As a stepping stone towards deprivileging the host's access to the
guest's vCPU structures, introduce some naive flush/sync routines to
copy most of the host vCPU into the shadow vCPU on vCPU run and back
again on return to EL1.

This allows us to run using the shadow structure when KVM is initialised
in protected mode.

Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/kvm/hyp/include/nvhe/pkvm.h |  4 ++
 arch/arm64/kvm/hyp/nvhe/hyp-main.c     | 84 +++++++++++++++++++++++++-
 arch/arm64/kvm/hyp/nvhe/pkvm.c         | 28 +++++++++
 3 files changed, 114 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
index c0e32a750b6e..0edb3faa4067 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
@@ -63,4 +63,8 @@ int __pkvm_init_shadow(struct kvm *kvm, unsigned long shadow_hva,
 		       size_t shadow_size, unsigned long pgd_hva);
 int __pkvm_teardown_shadow(unsigned int shadow_handle);
 
+struct kvm_shadow_vcpu_state *
+pkvm_load_shadow_vcpu_state(unsigned int shadow_handle, unsigned int vcpu_idx);
+void pkvm_put_shadow_vcpu_state(struct kvm_shadow_vcpu_state *shadow_state);
+
 #endif /* __ARM64_KVM_NVHE_PKVM_H__ */
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index a1fbd11c8041..39d66c7b0560 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -22,11 +22,91 @@ DEFINE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
 
 void __kvm_hyp_host_forward_smc(struct kvm_cpu_context *host_ctxt);
 
+static void flush_shadow_state(struct kvm_shadow_vcpu_state *shadow_state)
+{
+	struct kvm_vcpu *shadow_vcpu = &shadow_state->shadow_vcpu;
+	struct kvm_vcpu *host_vcpu = shadow_state->host_vcpu;
+
+	shadow_vcpu->arch.ctxt		= host_vcpu->arch.ctxt;
+
+	shadow_vcpu->arch.sve_state	= kern_hyp_va(host_vcpu->arch.sve_state);
+	shadow_vcpu->arch.sve_max_vl	= host_vcpu->arch.sve_max_vl;
+
+	shadow_vcpu->arch.hw_mmu	= host_vcpu->arch.hw_mmu;
+
+	shadow_vcpu->arch.hcr_el2	= host_vcpu->arch.hcr_el2;
+	shadow_vcpu->arch.mdcr_el2	= host_vcpu->arch.mdcr_el2;
+	shadow_vcpu->arch.cptr_el2	= host_vcpu->arch.cptr_el2;
+
+	shadow_vcpu->arch.iflags	= host_vcpu->arch.iflags;
+	shadow_vcpu->arch.fp_state	= host_vcpu->arch.fp_state;
+
+	shadow_vcpu->arch.debug_ptr	= kern_hyp_va(host_vcpu->arch.debug_ptr);
+	shadow_vcpu->arch.host_fpsimd_state = host_vcpu->arch.host_fpsimd_state;
+
+	shadow_vcpu->arch.vsesr_el2	= host_vcpu->arch.vsesr_el2;
+
+	shadow_vcpu->arch.vgic_cpu.vgic_v3 = host_vcpu->arch.vgic_cpu.vgic_v3;
+}
+
+static void sync_shadow_state(struct kvm_shadow_vcpu_state *shadow_state)
+{
+	struct kvm_vcpu *shadow_vcpu = &shadow_state->shadow_vcpu;
+	struct kvm_vcpu *host_vcpu = shadow_state->host_vcpu;
+	struct vgic_v3_cpu_if *shadow_cpu_if = &shadow_vcpu->arch.vgic_cpu.vgic_v3;
+	struct vgic_v3_cpu_if *host_cpu_if = &host_vcpu->arch.vgic_cpu.vgic_v3;
+	unsigned int i;
+
+	host_vcpu->arch.ctxt		= shadow_vcpu->arch.ctxt;
+
+	host_vcpu->arch.hcr_el2		= shadow_vcpu->arch.hcr_el2;
+	host_vcpu->arch.cptr_el2	= shadow_vcpu->arch.cptr_el2;
+
+	host_vcpu->arch.fault		= shadow_vcpu->arch.fault;
+
+	host_vcpu->arch.iflags		= shadow_vcpu->arch.iflags;
+	host_vcpu->arch.fp_state	= shadow_vcpu->arch.fp_state;
+
+	host_cpu_if->vgic_hcr		= shadow_cpu_if->vgic_hcr;
+	for (i = 0; i < shadow_cpu_if->used_lrs; ++i)
+		host_cpu_if->vgic_lr[i] = shadow_cpu_if->vgic_lr[i];
+}
+
 static void handle___kvm_vcpu_run(struct kvm_cpu_context *host_ctxt)
 {
-	DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
+	DECLARE_REG(struct kvm_vcpu *, host_vcpu, host_ctxt, 1);
+	int ret;
+
+	host_vcpu = kern_hyp_va(host_vcpu);
+
+	if (unlikely(is_protected_kvm_enabled())) {
+		struct kvm_shadow_vcpu_state *shadow_state;
+		struct kvm_vcpu *shadow_vcpu;
+		struct kvm *host_kvm;
+		unsigned int handle;
+
+		host_kvm = kern_hyp_va(host_vcpu->kvm);
+		handle = host_kvm->arch.pkvm.shadow_handle;
+		shadow_state = pkvm_load_shadow_vcpu_state(handle,
+							   host_vcpu->vcpu_idx);
+		if (!shadow_state) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		shadow_vcpu = &shadow_state->shadow_vcpu;
+		flush_shadow_state(shadow_state);
+
+		ret = __kvm_vcpu_run(shadow_vcpu);
+
+		sync_shadow_state(shadow_state);
+		pkvm_put_shadow_vcpu_state(shadow_state);
+	} else {
+		ret = __kvm_vcpu_run(host_vcpu);
+	}
 
-	cpu_reg(host_ctxt, 1) =  __kvm_vcpu_run(kern_hyp_va(vcpu));
+out:
+	cpu_reg(host_ctxt, 1) =  ret;
 }
 
 static void handle___kvm_adjust_pc(struct kvm_cpu_context *host_ctxt)
diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index 571334fd58ff..bf92f4443c92 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -247,6 +247,33 @@ static struct kvm_shadow_vm *find_shadow_by_handle(unsigned int shadow_handle)
 	return shadow_table[shadow_idx];
 }
 
+struct kvm_shadow_vcpu_state *
+pkvm_load_shadow_vcpu_state(unsigned int shadow_handle, unsigned int vcpu_idx)
+{
+	struct kvm_shadow_vcpu_state *shadow_state = NULL;
+	struct kvm_shadow_vm *vm;
+
+	hyp_spin_lock(&shadow_lock);
+	vm = find_shadow_by_handle(shadow_handle);
+	if (!vm || vm->kvm.created_vcpus <= vcpu_idx)
+		goto unlock;
+
+	shadow_state = &vm->shadow_vcpu_states[vcpu_idx];
+	hyp_page_ref_inc(hyp_virt_to_page(vm));
+unlock:
+	hyp_spin_unlock(&shadow_lock);
+	return shadow_state;
+}
+
+void pkvm_put_shadow_vcpu_state(struct kvm_shadow_vcpu_state *shadow_state)
+{
+	struct kvm_shadow_vm *vm = shadow_state->shadow_vm;
+
+	hyp_spin_lock(&shadow_lock);
+	hyp_page_ref_dec(hyp_virt_to_page(vm));
+	hyp_spin_unlock(&shadow_lock);
+}
+
 static void unpin_host_vcpus(struct kvm_shadow_vcpu_state *shadow_vcpu_states,
 			     unsigned int nr_vcpus)
 {
@@ -304,6 +331,7 @@ static int init_shadow_structs(struct kvm *kvm, struct kvm_shadow_vm *vm,
 		shadow_vcpu->vcpu_idx = i;
 
 		shadow_vcpu->arch.hw_mmu = &vm->kvm.arch.mmu;
+		shadow_vcpu->arch.cflags = READ_ONCE(host_vcpu->arch.cflags);
 	}
 
 	return 0;
-- 
2.37.0.rc0.161.g10f37bed90-goog