KVM: arm64: Introduce hyp context

During __guest_enter, save and restore from a new hyp context rather
than the host context. This is preparation for separation of the hyp and
host context in nVHE.
Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200915104643.2543892-9-ascull@google.com

arch/arm64/include/asm/kvm_hyp.h

@@ -12,6 +12,7 @@
 #include <asm/alternative.h>
 #include <asm/sysreg.h>
 
+DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
 DECLARE_PER_CPU(unsigned long, kvm_hyp_vector);
 
 #define read_sysreg_elx(r,nvh,vh)					\
@@ -89,7 +90,7 @@ void activate_traps_vhe_load(struct kvm_vcpu *vcpu);
 void deactivate_traps_vhe_put(void);
 #endif
 
-u64 __guest_enter(struct kvm_vcpu *vcpu, struct kvm_cpu_context *host_ctxt);
+u64 __guest_enter(struct kvm_vcpu *vcpu);
 
 void __noreturn hyp_panic(void);
 #ifdef __KVM_NVHE_HYPERVISOR__

arch/arm64/kernel/image-vars.h

@@ -71,6 +71,7 @@ KVM_NVHE_ALIAS(kvm_update_va_mask);
 /* Global kernel state accessed by nVHE hyp code. */
 KVM_NVHE_ALIAS(arm64_ssbd_callback_required);
 KVM_NVHE_ALIAS(kvm_host_data);
+KVM_NVHE_ALIAS(kvm_hyp_ctxt);
 KVM_NVHE_ALIAS(kvm_hyp_vector);
 KVM_NVHE_ALIAS(kvm_vgic_global_state);
 

arch/arm64/kvm/arm.c

@@ -47,6 +47,7 @@ __asm__(".arch_extension	virt");
 #endif
 
 DEFINE_PER_CPU(struct kvm_host_data, kvm_host_data);
+DEFINE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
 DEFINE_PER_CPU(unsigned long, kvm_hyp_vector);
 static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
 
@@ -1542,6 +1543,7 @@ static int init_hyp_mode(void)
 
 	for_each_possible_cpu(cpu) {
 		struct kvm_host_data *cpu_data;
+		struct kvm_cpu_context *hyp_ctxt;
 		unsigned long *vector;
 
 		cpu_data = per_cpu_ptr(&kvm_host_data, cpu);
@@ -1552,6 +1554,14 @@ static int init_hyp_mode(void)
 			goto out_err;
 		}
 
+		hyp_ctxt = per_cpu_ptr(&kvm_hyp_ctxt, cpu);
+		err = create_hyp_mappings(hyp_ctxt, hyp_ctxt + 1, PAGE_HYP);
+
+		if (err) {
+			kvm_err("Cannot map hyp context: %d\n", err);
+			goto out_err;
+		}
+
 		vector = per_cpu_ptr(&kvm_hyp_vector, cpu);
 		err = create_hyp_mappings(vector, vector + 1, PAGE_HYP);
 

arch/arm64/kvm/hyp/entry.S

@@ -57,15 +57,15 @@
 .endm
 
 /*
- * u64 __guest_enter(struct kvm_vcpu *vcpu,
- *		     struct kvm_cpu_context *host_ctxt);
+ * u64 __guest_enter(struct kvm_vcpu *vcpu);
  */
 SYM_FUNC_START(__guest_enter)
 	// x0: vcpu
-	// x1: host context
-	// x2-x17: clobbered by macros
+	// x1-x17: clobbered by macros
 	// x29: guest context
 
+	hyp_adr_this_cpu x1, kvm_hyp_ctxt, x2
+
 	// Store the host regs
 	save_callee_saved_regs x1
 
@@ -148,7 +148,7 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
 	// Store the guest's sp_el0
 	save_sp_el0	x1, x2
 
-	get_host_ctxt	x2, x3
+	hyp_adr_this_cpu x2, kvm_hyp_ctxt, x3
 
 	// Macro ptrauth_switch_to_guest format:
 	// 	ptrauth_switch_to_host(guest cxt, host cxt, tmp1, tmp2, tmp3)

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

@@ -381,7 +381,7 @@ static inline bool __hyp_handle_ptrauth(struct kvm_vcpu *vcpu)
 	    !esr_is_ptrauth_trap(kvm_vcpu_get_esr(vcpu)))
 		return false;
 
-	ctxt = &__hyp_this_cpu_ptr(kvm_host_data)->host_ctxt;
+	ctxt = __hyp_this_cpu_ptr(kvm_hyp_ctxt);
 	__ptrauth_save_key(ctxt, APIA);
 	__ptrauth_save_key(ctxt, APIB);
 	__ptrauth_save_key(ctxt, APDA);

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

@@ -209,7 +209,7 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 
 	do {
 		/* Jump in the fire! */
-		exit_code = __guest_enter(vcpu, host_ctxt);
+		exit_code = __guest_enter(vcpu);
 
 		/* And we're baaack! */
 	} while (fixup_guest_exit(vcpu, &exit_code));

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

@@ -135,7 +135,7 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
 
 	do {
 		/* Jump in the fire! */
-		exit_code = __guest_enter(vcpu, host_ctxt);
+		exit_code = __guest_enter(vcpu);
 
 		/* And we're baaack! */
 	} while (fixup_guest_exit(vcpu, &exit_code));