arm64: KVM: Implement the core world switch

Implement the core of the world switch in C. Not everything is there
yet, and there is nothing to re-enter the world switch either.

But this already outlines the code structure well enough.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

arch/arm64/kvm/hyp/Makefile

@@ -8,3 +8,4 @@ obj-$(CONFIG_KVM_ARM_HOST) += timer-sr.o
 obj-$(CONFIG_KVM_ARM_HOST) += sysreg-sr.o
 obj-$(CONFIG_KVM_ARM_HOST) += debug-sr.o
 obj-$(CONFIG_KVM_ARM_HOST) += entry.o
+obj-$(CONFIG_KVM_ARM_HOST) += switch.o

arch/arm64/kvm/hyp/switch.c

+/*
+ * Copyright (C) 2015 - ARM Ltd
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "hyp.h"
+
+static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
+{
+	u64 val;
+
+	/*
+	 * We are about to set CPTR_EL2.TFP to trap all floating point
+	 * register accesses to EL2, however, the ARM ARM clearly states that
+	 * traps are only taken to EL2 if the operation would not otherwise
+	 * trap to EL1.  Therefore, always make sure that for 32-bit guests,
+	 * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
+	 */
+	val = vcpu->arch.hcr_el2;
+	if (!(val & HCR_RW)) {
+		write_sysreg(1 << 30, fpexc32_el2);
+		isb();
+	}
+	write_sysreg(val, hcr_el2);
+	/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
+	write_sysreg(1 << 15, hstr_el2);
+	write_sysreg(CPTR_EL2_TTA | CPTR_EL2_TFP, cptr_el2);
+	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
+}
+
+static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
+{
+	write_sysreg(HCR_RW, hcr_el2);
+	write_sysreg(0, hstr_el2);
+	write_sysreg(read_sysreg(mdcr_el2) & MDCR_EL2_HPMN_MASK, mdcr_el2);
+	write_sysreg(0, cptr_el2);
+}
+
+static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
+	write_sysreg(kvm->arch.vttbr, vttbr_el2);
+}
+
+static void __hyp_text __deactivate_vm(struct kvm_vcpu *vcpu)
+{
+	write_sysreg(0, vttbr_el2);
+}
+
+static hyp_alternate_select(__vgic_call_save_state,
+			    __vgic_v2_save_state, __vgic_v3_save_state,
+			    ARM64_HAS_SYSREG_GIC_CPUIF);
+
+static hyp_alternate_select(__vgic_call_restore_state,
+			    __vgic_v2_restore_state, __vgic_v3_restore_state,
+			    ARM64_HAS_SYSREG_GIC_CPUIF);
+
+static void __hyp_text __vgic_save_state(struct kvm_vcpu *vcpu)
+{
+	__vgic_call_save_state()(vcpu);
+	write_sysreg(read_sysreg(hcr_el2) & ~HCR_INT_OVERRIDE, hcr_el2);
+}
+
+static void __hyp_text __vgic_restore_state(struct kvm_vcpu *vcpu)
+{
+	u64 val;
+
+	val = read_sysreg(hcr_el2);
+	val |= 	HCR_INT_OVERRIDE;
+	val |= vcpu->arch.irq_lines;
+	write_sysreg(val, hcr_el2);
+
+	__vgic_call_restore_state()(vcpu);
+}
+
+int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpu_context *host_ctxt;
+	struct kvm_cpu_context *guest_ctxt;
+	u64 exit_code;
+
+	vcpu = kern_hyp_va(vcpu);
+	write_sysreg(vcpu, tpidr_el2);
+
+	host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
+	guest_ctxt = &vcpu->arch.ctxt;
+
+	__sysreg_save_state(host_ctxt);
+	__debug_cond_save_host_state(vcpu);
+
+	__activate_traps(vcpu);
+	__activate_vm(vcpu);
+
+	__vgic_restore_state(vcpu);
+	__timer_restore_state(vcpu);
+
+	/*
+	 * We must restore the 32-bit state before the sysregs, thanks
+	 * to Cortex-A57 erratum #852523.
+	 */
+	__sysreg32_restore_state(vcpu);
+	__sysreg_restore_state(guest_ctxt);
+	__debug_restore_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
+
+	/* Jump in the fire! */
+	exit_code = __guest_enter(vcpu, host_ctxt);
+	/* And we're baaack! */
+
+	__sysreg_save_state(guest_ctxt);
+	__sysreg32_save_state(vcpu);
+	__timer_save_state(vcpu);
+	__vgic_save_state(vcpu);
+
+	__deactivate_traps(vcpu);
+	__deactivate_vm(vcpu);
+
+	__sysreg_restore_state(host_ctxt);
+
+	__debug_save_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
+	__debug_cond_restore_host_state(vcpu);
+
+	return exit_code;
+}