KVM: arm64: Add accessor for per-CPU state

In order to facilitate the introduction of new per-CPU state,
add a new host_data_ptr() helped that hides some of the per-CPU
verbosity, and make it easier to move that state around in the
future.
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/include/asm/kvm_host.h

@@ -530,6 +530,17 @@ struct kvm_cpu_context {
 	u64 *vncr_array;
 };
 
+/*
+ * This structure is instantiated on a per-CPU basis, and contains
+ * data that is:
+ *
+ * - tied to a single physical CPU, and
+ * - either have a lifetime that does not extend past vcpu_put()
+ * - or is an invariant for the lifetime of the system
+ *
+ * Use host_data_ptr(field) as a way to access a pointer to such a
+ * field.
+ */
 struct kvm_host_data {
 	struct kvm_cpu_context host_ctxt;
 };
@@ -1168,6 +1179,32 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
 
 DECLARE_KVM_HYP_PER_CPU(struct kvm_host_data, kvm_host_data);
 
+/*
+ * How we access per-CPU host data depends on the where we access it from,
+ * and the mode we're in:
+ *
+ * - VHE and nVHE hypervisor bits use their locally defined instance
+ *
+ * - the rest of the kernel use either the VHE or nVHE one, depending on
+ *   the mode we're running in.
+ *
+ *   Unless we're in protected mode, fully deprivileged, and the nVHE
+ *   per-CPU stuff is exclusively accessible to the protected EL2 code.
+ *   In this case, the EL1 code uses the *VHE* data as its private state
+ *   (which makes sense in a way as there shouldn't be any shared state
+ *   between the host and the hypervisor).
+ *
+ * Yes, this is all totally trivial. Shoot me now.
+ */
+#if defined(__KVM_NVHE_HYPERVISOR__) || defined(__KVM_VHE_HYPERVISOR__)
+#define host_data_ptr(f)	(&this_cpu_ptr(&kvm_host_data)->f)
+#else
+#define host_data_ptr(f)						\
+	(static_branch_unlikely(&kvm_protected_mode_initialized) ?	\
+	 &this_cpu_ptr(&kvm_host_data)->f :				\
+	 &this_cpu_ptr_hyp_sym(kvm_host_data)->f)
+#endif
+
 static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt)
 {
 	/* The host's MPIDR is immutable, so let's set it up at boot time */

arch/arm64/kvm/arm.c

@@ -1971,7 +1971,7 @@ static void cpu_set_hyp_vector(void)
 
 static void cpu_hyp_init_context(void)
 {
-	kvm_init_host_cpu_context(&this_cpu_ptr_hyp_sym(kvm_host_data)->host_ctxt);
+	kvm_init_host_cpu_context(host_data_ptr(host_ctxt));
 
 	if (!is_kernel_in_hyp_mode())
 		cpu_init_hyp_mode();

arch/arm64/kvm/hyp/include/hyp/debug-sr.h

@@ -135,7 +135,7 @@ static inline void __debug_switch_to_guest_common(struct kvm_vcpu *vcpu)
 	if (!vcpu_get_flag(vcpu, DEBUG_DIRTY))
 		return;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 	guest_ctxt = &vcpu->arch.ctxt;
 	host_dbg = &vcpu->arch.host_debug_state.regs;
 	guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);
@@ -154,7 +154,7 @@ static inline void __debug_switch_to_host_common(struct kvm_vcpu *vcpu)
 	if (!vcpu_get_flag(vcpu, DEBUG_DIRTY))
 		return;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 	guest_ctxt = &vcpu->arch.ctxt;
 	host_dbg = &vcpu->arch.host_debug_state.regs;
 	guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);

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

@@ -155,7 +155,7 @@ static inline bool cpu_has_amu(void)
 
 static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 {
-	struct kvm_cpu_context *hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	struct kvm_cpu_context *hctxt = host_data_ptr(host_ctxt);
 	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
 
 	CHECK_FGT_MASKS(HFGRTR_EL2);
@@ -191,7 +191,7 @@ static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 
 static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 {
-	struct kvm_cpu_context *hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	struct kvm_cpu_context *hctxt = host_data_ptr(host_ctxt);
 	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
 
 	if (!cpus_have_final_cap(ARM64_HAS_FGT))
@@ -226,7 +226,7 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
 
 		write_sysreg(0, pmselr_el0);
 
-		hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+		hctxt = host_data_ptr(host_ctxt);
 		ctxt_sys_reg(hctxt, PMUSERENR_EL0) = read_sysreg(pmuserenr_el0);
 		write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
 		vcpu_set_flag(vcpu, PMUSERENR_ON_CPU);
@@ -260,7 +260,7 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
 	if (kvm_arm_support_pmu_v3()) {
 		struct kvm_cpu_context *hctxt;
 
-		hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+		hctxt = host_data_ptr(host_ctxt);
 		write_sysreg(ctxt_sys_reg(hctxt, PMUSERENR_EL0), pmuserenr_el0);
 		vcpu_clear_flag(vcpu, PMUSERENR_ON_CPU);
 	}

arch/arm64/kvm/hyp/nvhe/psci-relay.c

@@ -205,7 +205,7 @@ asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
 	struct psci_boot_args *boot_args;
 	struct kvm_cpu_context *host_ctxt;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 
 	if (is_cpu_on)
 		boot_args = this_cpu_ptr(&cpu_on_args);

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

@@ -257,8 +257,7 @@ static int fix_hyp_pgtable_refcnt(void)
 
 void __noreturn __pkvm_init_finalise(void)
 {
-	struct kvm_host_data *host_data = this_cpu_ptr(&kvm_host_data);
-	struct kvm_cpu_context *host_ctxt = &host_data->host_ctxt;
+	struct kvm_cpu_context *host_ctxt = host_data_ptr(host_ctxt);
 	unsigned long nr_pages, reserved_pages, pfn;
 	int ret;
 

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

@@ -264,7 +264,7 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 		pmr_sync();
 	}
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 	host_ctxt->__hyp_running_vcpu = vcpu;
 	guest_ctxt = &vcpu->arch.ctxt;
 
@@ -367,7 +367,7 @@ asmlinkage void __noreturn hyp_panic(void)
 	struct kvm_cpu_context *host_ctxt;
 	struct kvm_vcpu *vcpu;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 	vcpu = host_ctxt->__hyp_running_vcpu;
 
 	if (vcpu) {

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

@@ -221,7 +221,7 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
 	struct kvm_cpu_context *guest_ctxt;
 	u64 exit_code;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 	host_ctxt->__hyp_running_vcpu = vcpu;
 	guest_ctxt = &vcpu->arch.ctxt;
 
@@ -306,7 +306,7 @@ static void __hyp_call_panic(u64 spsr, u64 elr, u64 par)
 	struct kvm_cpu_context *host_ctxt;
 	struct kvm_vcpu *vcpu;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 	vcpu = host_ctxt->__hyp_running_vcpu;
 
 	__deactivate_traps(vcpu);

arch/arm64/kvm/hyp/vhe/sysreg-sr.c

@@ -67,7 +67,7 @@ void __vcpu_load_switch_sysregs(struct kvm_vcpu *vcpu)
 	struct kvm_cpu_context *guest_ctxt = &vcpu->arch.ctxt;
 	struct kvm_cpu_context *host_ctxt;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 	__sysreg_save_user_state(host_ctxt);
 
 	/*
@@ -110,7 +110,7 @@ void __vcpu_put_switch_sysregs(struct kvm_vcpu *vcpu)
 	struct kvm_cpu_context *guest_ctxt = &vcpu->arch.ctxt;
 	struct kvm_cpu_context *host_ctxt;
 
-	host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	host_ctxt = host_data_ptr(host_ctxt);
 
 	__sysreg_save_el1_state(guest_ctxt);
 	__sysreg_save_user_state(guest_ctxt);

arch/arm64/kvm/pmu.c

@@ -232,7 +232,7 @@ bool kvm_set_pmuserenr(u64 val)
 	if (!vcpu || !vcpu_get_flag(vcpu, PMUSERENR_ON_CPU))
 		return false;
 
-	hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
+	hctxt = host_data_ptr(host_ctxt);
 	ctxt_sys_reg(hctxt, PMUSERENR_EL0) = val;
 	return true;
 }