KVM: arm64: Implement PV_TIME_FEATURES call

This provides a mechanism for querying which paravirtualized time
features are available in this hypervisor.

Also add the header file which defines the ABI for the paravirtualized
time features we're about to add.

Signed-off-by: Steven Price <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>

arch/arm/include/asm/kvm_host.h

···
 #ifndef __ARM_KVM_HOST_H__
 #define __ARM_KVM_HOST_H__
 
+#include <linux/arm-smccc.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/kvm_types.h>
···
 
 int kvm_perf_init(void);
 int kvm_perf_teardown(void);
+
+static inline long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
+{
+	return SMCCC_RET_NOT_SUPPORTED;
+}
 
 void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
 

arch/arm64/include/asm/kvm_host.h

···
 int kvm_perf_init(void);
 int kvm_perf_teardown(void);
 
+long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu);
+
 void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
 
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);

arch/arm64/include/asm/pvclock-abi.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 Arm Ltd. */
+
+#ifndef __ASM_PVCLOCK_ABI_H
+#define __ASM_PVCLOCK_ABI_H
+
+/* The below structure is defined in ARM DEN0057A */
+
+struct pvclock_vcpu_stolen_time {
+	__le32 revision;
+	__le32 attributes;
+	__le64 stolen_time;
+	/* Structure must be 64 byte aligned, pad to that size */
+	u8 padding[48];
+} __packed;
+
+#endif

arch/arm64/kvm/Makefile

···
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hypercalls.o
+kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/pvtime.o
 
 kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
 kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o

include/linux/arm-smccc.h

···
 #define ARM_SMCCC_OWNER_SIP		2
 #define ARM_SMCCC_OWNER_OEM		3
 #define ARM_SMCCC_OWNER_STANDARD	4
+#define ARM_SMCCC_OWNER_STANDARD_HYP	5
 #define ARM_SMCCC_OWNER_TRUSTED_APP	48
 #define ARM_SMCCC_OWNER_TRUSTED_APP_END	49
 #define ARM_SMCCC_OWNER_TRUSTED_OS	50
···
 #define SMCCC_RET_SUCCESS			0
 #define SMCCC_RET_NOT_SUPPORTED			-1
 #define SMCCC_RET_NOT_REQUIRED			-2
+
+/* Paravirtualised time calls (defined by ARM DEN0057A) */
+#define ARM_SMCCC_HV_PV_TIME_FEATURES				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_64,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   0x20)
+
+#define ARM_SMCCC_HV_PV_TIME_ST					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_64,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   0x21)
 
 #endif /*__ASSEMBLY__*/
 #endif /*__LINUX_ARM_SMCCC_H*/

virt/kvm/arm/hypercalls.c

···
 int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 {
 	u32 func_id = smccc_get_function(vcpu);
-	u32 val = SMCCC_RET_NOT_SUPPORTED;
+	long val = SMCCC_RET_NOT_SUPPORTED;
 	u32 feature;
 
 	switch (func_id) {
···
 				break;
 			}
 			break;
+		case ARM_SMCCC_HV_PV_TIME_FEATURES:
+			val = SMCCC_RET_SUCCESS;
+			break;
 		}
+		break;
+	case ARM_SMCCC_HV_PV_TIME_FEATURES:
+		val = kvm_hypercall_pv_features(vcpu);
 		break;
 	default:
 		return kvm_psci_call(vcpu);

virt/kvm/arm/pvtime.c

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2019 Arm Ltd.
+
+#include <linux/arm-smccc.h>
+
+#include <kvm/arm_hypercalls.h>
+
+long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
+{
+	u32 feature = smccc_get_arg1(vcpu);
+	long val = SMCCC_RET_NOT_SUPPORTED;
+
+	switch (feature) {
+	case ARM_SMCCC_HV_PV_TIME_FEATURES:
+		val = SMCCC_RET_SUCCESS;
+		break;
+	}
+
+	return val;
+}