LoongArch: KVM: Add PV steal time support in host side

Add ParaVirt steal time feature in host side, VM can search supported
features provided by KVM hypervisor, a feature KVM_FEATURE_STEAL_TIME
is added here. Like x86, steal time structure is saved in guest memory,
one hypercall function KVM_HCALL_FUNC_NOTIFY is added to notify KVM to
enable this feature.

One CPU attr ioctl command KVM_LOONGARCH_VCPU_PVTIME_CTRL is added to
save and restore the base address of steal time structure when a VM is
migrated.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/kvm_host.h

@@ -31,6 +31,7 @@
 
 #define KVM_HALT_POLL_NS_DEFAULT	500000
 #define KVM_REQ_TLB_FLUSH_GPA		KVM_ARCH_REQ(0)
+#define KVM_REQ_STEAL_UPDATE		KVM_ARCH_REQ(1)
 
 #define KVM_GUESTDBG_SW_BP_MASK		\
 	(KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)
@@ -206,6 +207,13 @@ struct kvm_vcpu_arch {
 	struct kvm_mp_state mp_state;
 	/* cpucfg */
 	u32 cpucfg[KVM_MAX_CPUCFG_REGS];
+
+	/* paravirt steal time */
+	struct {
+		u64 guest_addr;
+		u64 last_steal;
+		struct gfn_to_hva_cache cache;
+	} st;
 };
 
 static inline unsigned long readl_sw_gcsr(struct loongarch_csrs *csr, int reg)

arch/loongarch/include/asm/kvm_para.h

@@ -14,6 +14,7 @@
 
 #define KVM_HCALL_SERVICE		HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SERVICE)
 #define  KVM_HCALL_FUNC_IPI		1
+#define  KVM_HCALL_FUNC_NOTIFY		2
 
 #define KVM_HCALL_SWDBG			HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SWDBG)
 
@@ -24,6 +25,16 @@
 #define KVM_HCALL_INVALID_CODE		-1UL
 #define KVM_HCALL_INVALID_PARAMETER	-2UL
 
+#define KVM_STEAL_PHYS_VALID		BIT_ULL(0)
+#define KVM_STEAL_PHYS_MASK		GENMASK_ULL(63, 6)
+
+struct kvm_steal_time {
+	__u64 steal;
+	__u32 version;
+	__u32 flags;
+	__u32 pad[12];
+};
+
 /*
  * Hypercall interface for KVM hypervisor
  *

arch/loongarch/include/asm/kvm_vcpu.h

@@ -120,4 +120,9 @@ static inline void kvm_write_reg(struct kvm_vcpu *vcpu, int num, unsigned long v
 	vcpu->arch.gprs[num] = val;
 }
 
+static inline bool kvm_pvtime_supported(void)
+{
+	return !!sched_info_on();
+}
+
 #endif /* __ASM_LOONGARCH_KVM_VCPU_H__ */

arch/loongarch/include/asm/loongarch.h

@@ -169,6 +169,7 @@
 #define  KVM_SIGNATURE			"KVM\0"
 #define CPUCFG_KVM_FEATURE		(CPUCFG_KVM_BASE + 4)
 #define  KVM_FEATURE_IPI		BIT(1)
+#define  KVM_FEATURE_STEAL_TIME		BIT(2)
 
 #ifndef __ASSEMBLY__
 

arch/loongarch/include/uapi/asm/kvm.h

@@ -81,7 +81,11 @@ struct kvm_fpu {
 #define LOONGARCH_REG_64(TYPE, REG)	(TYPE | KVM_REG_SIZE_U64 | (REG << LOONGARCH_REG_SHIFT))
 #define KVM_IOC_CSRID(REG)		LOONGARCH_REG_64(KVM_REG_LOONGARCH_CSR, REG)
 #define KVM_IOC_CPUCFG(REG)		LOONGARCH_REG_64(KVM_REG_LOONGARCH_CPUCFG, REG)
+
+/* Device Control API on vcpu fd */
 #define KVM_LOONGARCH_VCPU_CPUCFG	0
+#define KVM_LOONGARCH_VCPU_PVTIME_CTRL	1
+#define  KVM_LOONGARCH_VCPU_PVTIME_GPA	0
 
 struct kvm_debug_exit_arch {
 };

arch/loongarch/kvm/Kconfig

@@ -29,6 +29,7 @@ config KVM
 	select KVM_MMIO
 	select HAVE_KVM_READONLY_MEM
 	select KVM_XFER_TO_GUEST_WORK
+	select SCHED_INFO
 	help
 	  Support hosting virtualized guest machines using
 	  hardware virtualization extensions. You will need

arch/loongarch/kvm/exit.c

@@ -24,7 +24,7 @@
 static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
 {
 	int rd, rj;
-	unsigned int index;
+	unsigned int index, ret;
 
 	if (inst.reg2_format.opcode != cpucfg_op)
 		return EMULATE_FAIL;
@@ -50,7 +50,10 @@ static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
 		vcpu->arch.gprs[rd] = *(unsigned int *)KVM_SIGNATURE;
 		break;
 	case CPUCFG_KVM_FEATURE:
-		vcpu->arch.gprs[rd] = KVM_FEATURE_IPI;
+		ret = KVM_FEATURE_IPI;
+		if (kvm_pvtime_supported())
+			ret |= KVM_FEATURE_STEAL_TIME;
+		vcpu->arch.gprs[rd] = ret;
 		break;
 	default:
 		vcpu->arch.gprs[rd] = 0;
@@ -687,6 +690,34 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu)
 	return RESUME_GUEST;
 }
 
+static long kvm_save_notify(struct kvm_vcpu *vcpu)
+{
+	unsigned long id, data;
+
+	id   = kvm_read_reg(vcpu, LOONGARCH_GPR_A1);
+	data = kvm_read_reg(vcpu, LOONGARCH_GPR_A2);
+	switch (id) {
+	case KVM_FEATURE_STEAL_TIME:
+		if (!kvm_pvtime_supported())
+			return KVM_HCALL_INVALID_CODE;
+
+		if (data & ~(KVM_STEAL_PHYS_MASK | KVM_STEAL_PHYS_VALID))
+			return KVM_HCALL_INVALID_PARAMETER;
+
+		vcpu->arch.st.guest_addr = data;
+		if (!(data & KVM_STEAL_PHYS_VALID))
+			break;
+
+		vcpu->arch.st.last_steal = current->sched_info.run_delay;
+		kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
+		break;
+	default:
+		break;
+	};
+
+	return 0;
+};
+
 /*
  * kvm_handle_lsx_disabled() - Guest used LSX while disabled in root.
  * @vcpu:      Virtual CPU context.
@@ -758,6 +789,9 @@ static void kvm_handle_service(struct kvm_vcpu *vcpu)
 		kvm_send_pv_ipi(vcpu);
 		ret = KVM_HCALL_SUCCESS;
 		break;
+	case KVM_HCALL_FUNC_NOTIFY:
+		ret = kvm_save_notify(vcpu);
+		break;
 	default:
 		ret = KVM_HCALL_INVALID_CODE;
 		break;

arch/loongarch/kvm/vcpu.c

@@ -31,6 +31,50 @@ const struct kvm_stats_header kvm_vcpu_stats_header = {
 		       sizeof(kvm_vcpu_stats_desc),
 };
 
+static void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
+{
+	u32 version;
+	u64 steal;
+	gpa_t gpa;
+	struct kvm_memslots *slots;
+	struct kvm_steal_time __user *st;
+	struct gfn_to_hva_cache *ghc;
+
+	ghc = &vcpu->arch.st.cache;
+	gpa = vcpu->arch.st.guest_addr;
+	if (!(gpa & KVM_STEAL_PHYS_VALID))
+		return;
+
+	gpa &= KVM_STEAL_PHYS_MASK;
+	slots = kvm_memslots(vcpu->kvm);
+	if (slots->generation != ghc->generation || gpa != ghc->gpa) {
+		if (kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, gpa, sizeof(*st))) {
+			ghc->gpa = INVALID_GPA;
+			return;
+		}
+	}
+
+	st = (struct kvm_steal_time __user *)ghc->hva;
+	unsafe_get_user(version, &st->version, out);
+	if (version & 1)
+		version += 1; /* first time write, random junk */
+
+	version += 1;
+	unsafe_put_user(version, &st->version, out);
+	smp_wmb();
+
+	unsafe_get_user(steal, &st->steal, out);
+	steal += current->sched_info.run_delay - vcpu->arch.st.last_steal;
+	vcpu->arch.st.last_steal = current->sched_info.run_delay;
+	unsafe_put_user(steal, &st->steal, out);
+
+	smp_wmb();
+	version += 1;
+	unsafe_put_user(version, &st->version, out);
+out:
+	mark_page_dirty_in_slot(vcpu->kvm, ghc->memslot, gpa_to_gfn(ghc->gpa));
+}
+
 /*
  * kvm_check_requests - check and handle pending vCPU requests
  *
@@ -48,6 +92,9 @@ static int kvm_check_requests(struct kvm_vcpu *vcpu)
 	if (kvm_dirty_ring_check_request(vcpu))
 		return RESUME_HOST;
 
+	if (kvm_check_request(KVM_REQ_STEAL_UPDATE, vcpu))
+		kvm_update_stolen_time(vcpu);
+
 	return RESUME_GUEST;
 }
 
@@ -690,6 +737,16 @@ static int kvm_loongarch_cpucfg_has_attr(struct kvm_vcpu *vcpu,
 	return -ENXIO;
 }
 
+static int kvm_loongarch_pvtime_has_attr(struct kvm_vcpu *vcpu,
+					 struct kvm_device_attr *attr)
+{
+	if (!kvm_pvtime_supported() ||
+			attr->attr != KVM_LOONGARCH_VCPU_PVTIME_GPA)
+		return -ENXIO;
+
+	return 0;
+}
+
 static int kvm_loongarch_vcpu_has_attr(struct kvm_vcpu *vcpu,
 				       struct kvm_device_attr *attr)
 {
@@ -699,6 +756,9 @@ static int kvm_loongarch_vcpu_has_attr(struct kvm_vcpu *vcpu,
 	case KVM_LOONGARCH_VCPU_CPUCFG:
 		ret = kvm_loongarch_cpucfg_has_attr(vcpu, attr);
 		break;
+	case KVM_LOONGARCH_VCPU_PVTIME_CTRL:
+		ret = kvm_loongarch_pvtime_has_attr(vcpu, attr);
+		break;
 	default:
 		break;
 	}
@@ -706,7 +766,7 @@ static int kvm_loongarch_vcpu_has_attr(struct kvm_vcpu *vcpu,
 	return ret;
 }
 
-static int kvm_loongarch_get_cpucfg_attr(struct kvm_vcpu *vcpu,
+static int kvm_loongarch_cpucfg_get_attr(struct kvm_vcpu *vcpu,
 					 struct kvm_device_attr *attr)
 {
 	int ret = 0;
@@ -722,6 +782,23 @@ static int kvm_loongarch_get_cpucfg_attr(struct kvm_vcpu *vcpu,
 	return ret;
 }
 
+static int kvm_loongarch_pvtime_get_attr(struct kvm_vcpu *vcpu,
+					 struct kvm_device_attr *attr)
+{
+	u64 gpa;
+	u64 __user *user = (u64 __user *)attr->addr;
+
+	if (!kvm_pvtime_supported() ||
+			attr->attr != KVM_LOONGARCH_VCPU_PVTIME_GPA)
+		return -ENXIO;
+
+	gpa = vcpu->arch.st.guest_addr;
+	if (put_user(gpa, user))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int kvm_loongarch_vcpu_get_attr(struct kvm_vcpu *vcpu,
 				       struct kvm_device_attr *attr)
 {
@@ -729,7 +806,10 @@ static int kvm_loongarch_vcpu_get_attr(struct kvm_vcpu *vcpu,
 
 	switch (attr->group) {
 	case KVM_LOONGARCH_VCPU_CPUCFG:
-		ret = kvm_loongarch_get_cpucfg_attr(vcpu, attr);
+		ret = kvm_loongarch_cpucfg_get_attr(vcpu, attr);
+		break;
+	case KVM_LOONGARCH_VCPU_PVTIME_CTRL:
+		ret = kvm_loongarch_pvtime_get_attr(vcpu, attr);
 		break;
 	default:
 		break;
@@ -744,6 +824,43 @@ static int kvm_loongarch_cpucfg_set_attr(struct kvm_vcpu *vcpu,
 	return -ENXIO;
 }
 
+static int kvm_loongarch_pvtime_set_attr(struct kvm_vcpu *vcpu,
+					 struct kvm_device_attr *attr)
+{
+	int idx, ret = 0;
+	u64 gpa, __user *user = (u64 __user *)attr->addr;
+	struct kvm *kvm = vcpu->kvm;
+
+	if (!kvm_pvtime_supported() ||
+			attr->attr != KVM_LOONGARCH_VCPU_PVTIME_GPA)
+		return -ENXIO;
+
+	if (get_user(gpa, user))
+		return -EFAULT;
+
+	if (gpa & ~(KVM_STEAL_PHYS_MASK | KVM_STEAL_PHYS_VALID))
+		return -EINVAL;
+
+	if (!(gpa & KVM_STEAL_PHYS_VALID)) {
+		vcpu->arch.st.guest_addr = gpa;
+		return 0;
+	}
+
+	/* Check the address is in a valid memslot */
+	idx = srcu_read_lock(&kvm->srcu);
+	if (kvm_is_error_hva(gfn_to_hva(kvm, gpa >> PAGE_SHIFT)))
+		ret = -EINVAL;
+	srcu_read_unlock(&kvm->srcu, idx);
+
+	if (!ret) {
+		vcpu->arch.st.guest_addr = gpa;
+		vcpu->arch.st.last_steal = current->sched_info.run_delay;
+		kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
+	}
+
+	return ret;
+}
+
 static int kvm_loongarch_vcpu_set_attr(struct kvm_vcpu *vcpu,
 				       struct kvm_device_attr *attr)
 {
@@ -753,6 +870,9 @@ static int kvm_loongarch_vcpu_set_attr(struct kvm_vcpu *vcpu,
 	case KVM_LOONGARCH_VCPU_CPUCFG:
 		ret = kvm_loongarch_cpucfg_set_attr(vcpu, attr);
 		break;
+	case KVM_LOONGARCH_VCPU_PVTIME_CTRL:
+		ret = kvm_loongarch_pvtime_set_attr(vcpu, attr);
+		break;
 	default:
 		break;
 	}
@@ -1113,6 +1233,7 @@ static int _kvm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 
 	/* Control guest page CCA attribute */
 	change_csr_gcfg(CSR_GCFG_MATC_MASK, CSR_GCFG_MATC_ROOT);
+	kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
 
 	/* Don't bother restoring registers multiple times unless necessary */
 	if (vcpu->arch.aux_inuse & KVM_LARCH_HWCSR_USABLE)