KVM: arm64: timers: Allow userspace to set the global counter offset

And this is the moment you have all been waiting for: setting the counter offset from userspace. We expose a brand new capability that reports the ability to set the offset for both the virtual and physical sides. In keeping with the architecture, the offset is expressed as a delta that is substracted from the physical counter value. Once this new API is used, there is no going back, and the counters cannot be written to to set the offsets implicitly (the writes are instead ignored).

Marc Zyngier committed 3 years ago

Commit 30ec7991 parent 96906a95 files · +73 −5Browse files

Unified · Split

5 files

arch/arm64/include/asm/kvm_host.h +4 −0
arch/arm64/include/uapi/asm/kvm.h +9 −0
arch/arm64/kvm/arch_timer.c +49 −5
arch/arm64/kvm/arm.c +8 −0
include/uapi/linux/kvm.h +3 −0

arch/arm64/include/asm/kvm_host.h+4−0

@@ -221,6 +221,8 @@ struct kvm_arch { · 220 unmodified lines
221	221	#define KVM_ARCH_FLAG_EL1_32BIT 4
222	222	/* PSCI SYSTEM_SUSPEND enabled for the guest */
223	223	#define KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED 5
	224	+ /* VM counter offset */
	225	+#define KVM_ARCH_FLAG_VM_COUNTER_OFFSET 6
224	226
225	227	unsigned long flags;
226	228
@@ -1010,6 +1012,8 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu, · 783 unmodified lines
1010	1012
1011	1013	long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
1012	1014	struct kvm_arm_copy_mte_tags *copy_tags);
	1015	+int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm,
	1016	+ struct kvm_arm_counter_offset *offset);
1013	1017
1014	1018	/* Guest/host FPSIMD coordination helpers */
1015	1019	int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);

arch/arm64/include/uapi/asm/kvm.h+9−0

@@ -198,6 +198,15 @@ struct kvm_arm_copy_mte_tags { · 197 unmodified lines
198	198	__u64 reserved[2];
199	199	};
200	200
	201	+/*
	202	+ * Counter/Timer offset structure. Describe the virtual/physical offset.
	203	+ * To be used with KVM_ARM_SET_COUNTER_OFFSET.
	204	+ */
	205	+struct kvm_arm_counter_offset {
	206	+ __u64 counter_offset;
	207	+ __u64 reserved;
	208	+};
	209	+
201	210	#define KVM_ARM_TAGS_TO_GUEST 0
202	211	#define KVM_ARM_TAGS_FROM_GUEST 1
203	212

arch/arm64/kvm/arch_timer.c+49−5

@@ -851,9 +851,11 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu) · 850 unmodified lines
851	851	ptimer->vcpu = vcpu;
852	852	ptimer->offset.vm_offset = &vcpu->kvm->arch.timer_data.poffset;
853	853
854		− /* Synchronize cntvoff across all vtimers of a VM. */
855		− timer_set_offset(vtimer, kvm_phys_timer_read());
856		− timer_set_offset(ptimer, 0);
	854	+ /* Synchronize offsets across timers of a VM if not already provided */
	855	+ if (!test_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET, &vcpu->kvm->arch.flags)) {
	856	+ timer_set_offset(vtimer, kvm_phys_timer_read());
	857	+ timer_set_offset(ptimer, 0);
	858	+ }
857	859
858	860	hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
859	861	timer->bg_timer.function = kvm_bg_timer_expire;
@@ -897,8 +899,11 @@ int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value) · 37 unmodified lines
897	899	kvm_arm_timer_write(vcpu, timer, TIMER_REG_CTL, value);
898	900	break;
899	901	case KVM_REG_ARM_TIMER_CNT:
900		− timer = vcpu_vtimer(vcpu);
901		− timer_set_offset(timer, kvm_phys_timer_read() - value);
	902	+ if (!test_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET,
	903	+ &vcpu->kvm->arch.flags)) {
	904	+ timer = vcpu_vtimer(vcpu);
	905	+ timer_set_offset(timer, kvm_phys_timer_read() - value);
	906	+ }
902	907	break;
903	908	case KVM_REG_ARM_TIMER_CVAL:
904	909	timer = vcpu_vtimer(vcpu);
@@ -908,6 +913,13 @@ int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value) · 3 unmodified lines
908	913	timer = vcpu_ptimer(vcpu);
909	914	kvm_arm_timer_write(vcpu, timer, TIMER_REG_CTL, value);
910	915	break;
	916	+ case KVM_REG_ARM_PTIMER_CNT:
	917	+ if (!test_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET,
	918	+ &vcpu->kvm->arch.flags)) {
	919	+ timer = vcpu_ptimer(vcpu);
	920	+ timer_set_offset(timer, kvm_phys_timer_read() - value);
	921	+ }
	922	+ break;
911	923	case KVM_REG_ARM_PTIMER_CVAL:
912	924	timer = vcpu_ptimer(vcpu);
913	925	kvm_arm_timer_write(vcpu, timer, TIMER_REG_CVAL, value);
@@ -1443,3 +1455,35 @@ int kvm_arm_timer_has_attr(struct kvm_vcpu vcpu, struct kvm_device_attr attr) · 529 unmodified lines
1443	1455
1444	1456	return -ENXIO;
1445	1457	}
	1458	+
	1459	+int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm,
	1460	+ struct kvm_arm_counter_offset *offset)
	1461	+{
	1462	+ int ret = 0;
	1463	+
	1464	+ if (offset->reserved)
	1465	+ return -EINVAL;
	1466	+
	1467	+ mutex_lock(&kvm->lock);
	1468	+
	1469	+ if (lock_all_vcpus(kvm)) {
	1470	+ set_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET, &kvm->arch.flags);
	1471	+
	1472	+ /*
	1473	+ * If userspace decides to set the offset using this
	1474	+ * API rather than merely restoring the counter
	1475	+ * values, the offset applies to both the virtual and
	1476	+ * physical views.
	1477	+ */
	1478	+ kvm->arch.timer_data.voffset = offset->counter_offset;
	1479	+ kvm->arch.timer_data.poffset = offset->counter_offset;
	1480	+
	1481	+ unlock_all_vcpus(kvm);
	1482	+ } else {
	1483	+ ret = -EBUSY;
	1484	+ }
	1485	+
	1486	+ mutex_unlock(&kvm->lock);
	1487	+
	1488	+ return ret;
	1489	+}

arch/arm64/kvm/arm.c+8−0

@@ -220,6 +220,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) · 219 unmodified lines
220	220	case KVM_CAP_VCPU_ATTRIBUTES:
221	221	case KVM_CAP_PTP_KVM:
222	222	case KVM_CAP_ARM_SYSTEM_SUSPEND:
	223	+ case KVM_CAP_COUNTER_OFFSET:
223	224	r = 1;
224	225	break;
225	226	case KVM_CAP_SET_GUEST_DEBUG2:
@@ -1479,6 +1480,13 @@ long kvm_arch_vm_ioctl(struct file *filp, · 1253 unmodified lines
1479	1480	return -EFAULT;
1480	1481	return kvm_vm_ioctl_mte_copy_tags(kvm, &copy_tags);
1481	1482	}
	1483	+ case KVM_ARM_SET_COUNTER_OFFSET: {
	1484	+ struct kvm_arm_counter_offset offset;
	1485	+
	1486	+ if (copy_from_user(&offset, argp, sizeof(offset)))
	1487	+ return -EFAULT;
	1488	+ return kvm_vm_ioctl_set_counter_offset(kvm, &offset);
	1489	+ }
1482	1490	default:
1483	1491	return -EINVAL;
1484	1492	}

include/uapi/linux/kvm.h+3−0

@@ -1184,6 +1184,7 @@ struct kvm_ppc_resize_hpt { · 1183 unmodified lines
1184	1184	#define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224
1185	1185	#define KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP 225
1186	1186	#define KVM_CAP_PMU_EVENT_MASKED_EVENTS 226
	1187	+#define KVM_CAP_COUNTER_OFFSET 227
1187	1188
1188	1189	#ifdef KVM_CAP_IRQ_ROUTING
1189	1190
@@ -1543,6 +1544,8 @@ struct kvm_s390_ucas_mapping { · 353 unmodified lines
1543	1544	#define KVM_SET_PMU_EVENT_FILTER _IOW(KVMIO, 0xb2, struct kvm_pmu_event_filter)
1544	1545	#define KVM_PPC_SVM_OFF _IO(KVMIO, 0xb3)
1545	1546	#define KVM_ARM_MTE_COPY_TAGS _IOR(KVMIO, 0xb4, struct kvm_arm_copy_mte_tags)
	1547	+/* Available with KVM_CAP_COUNTER_OFFSET */
	1548	+#define KVM_ARM_SET_COUNTER_OFFSET _IOW(KVMIO, 0xb5, struct kvm_arm_counter_offset)
1546	1549
1547	1550	/* ioctl for vm fd */
1548	1551	#define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device)

KVM: arm64: timers: Allow userspace to set the global counter offset

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