@@ -4468,6 +4468,39 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
event/message pages and to enable/disable SynIC messages/events processing
in userspace.
+ /* KVM_EXIT_ARM_NISV */
+ struct {
+ __u64 esr_iss;
+ __u64 fault_ipa;
+ } arm_nisv;
+
+Used on arm and arm64 systems. If a guest accesses memory not in a memslot,
+KVM will typically return to userspace and ask it to do MMIO emulation on its
+behalf. However, for certain classes of instructions, no instruction decode
+(direction, length of memory access) is provided, and fetching and decoding
+the instruction from the VM is overly complicated to live in the kernel.
+
+Historically, when this situation occurred, KVM would print a warning and kill
+the VM. KVM assumed that if the guest accessed non-memslot memory, it was
+trying to do I/O, which just couldn't be emulated, and the warning message was
+phrased accordingly. However, what happened more often was that a guest bug
+caused access outside the guest memory areas which should lead to a more
+meaningful warning message and an external abort in the guest, if the access
+did not fall within an I/O window.
+
+Userspace implementations can query for KVM_CAP_ARM_NISV_TO_USER, and enable
+this capability at VM creation. Once this is done, these types of errors will
+instead return to userspace with KVM_EXIT_ARM_NISV, with the valid bits from
+the HSR (arm) and ESR_EL2 (arm64) in the esr_iss field, and the faulting IPA
+in the fault_ipa field. Userspace can either fix up the access if it's
+actually an I/O access by decoding the instruction from guest memory (if it's
+very brave) and continue executing the guest, or it can decide to suspend,
+dump, or restart the guest.
+
+Note that KVM does not skip the faulting instruction as it does for
+KVM_EXIT_MMIO, but userspace has to emulate any change to the processing state
+if it decides to decode and emulate the instruction.
+
/* Fix the size of the union. */
char padding[256];
};
@@ -162,6 +162,7 @@
#define HSR_ISV (_AC(1, UL) << HSR_ISV_SHIFT)
#define HSR_SRT_SHIFT (16)
#define HSR_SRT_MASK (0xf << HSR_SRT_SHIFT)
+#define HSR_CM (1 << 8)
#define HSR_FSC (0x3f)
#define HSR_FSC_TYPE (0x3c)
#define HSR_SSE (1 << 21)
@@ -167,6 +167,11 @@ static inline bool kvm_vcpu_dabt_isvalid(struct kvm_vcpu *vcpu)
return kvm_vcpu_get_hsr(vcpu) & HSR_ISV;
}
+static inline unsigned long kvm_vcpu_dabt_iss_nisv_sanitized(const struct kvm_vcpu *vcpu)
+{
+ return kvm_vcpu_get_hsr(vcpu) & (HSR_CM | HSR_WNR | HSR_FSC);
+}
+
static inline bool kvm_vcpu_dabt_iswrite(struct kvm_vcpu *vcpu)
{
return kvm_vcpu_get_hsr(vcpu) & HSR_WNR;
@@ -76,6 +76,14 @@ struct kvm_arch {
/* Mandated version of PSCI */
u32 psci_version;
+
+ /*
+ * If we encounter a data abort without valid instruction syndrome
+ * information, report this to user space. User space can (and
+ * should) opt in to this feature if KVM_CAP_ARM_NISV_TO_USER is
+ * supported.
+ */
+ bool return_nisv_io_abort_to_user;
};
#define KVM_NR_MEM_OBJS 40
@@ -258,6 +258,11 @@ static inline bool kvm_vcpu_dabt_isvalid(const struct kvm_vcpu *vcpu)
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_ISV);
}
+static inline unsigned long kvm_vcpu_dabt_iss_nisv_sanitized(const struct kvm_vcpu *vcpu)
+{
+ return kvm_vcpu_get_hsr(vcpu) & (ESR_ELx_CM | ESR_ELx_WNR | ESR_ELx_FSC);
+}
+
static inline bool kvm_vcpu_dabt_issext(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SSE);
@@ -83,6 +83,14 @@ struct kvm_arch {
/* Mandated version of PSCI */
u32 psci_version;
+
+ /*
+ * If we encounter a data abort without valid instruction syndrome
+ * information, report this to user space. User space can (and
+ * should) opt in to this feature if KVM_CAP_ARM_NISV_TO_USER is
+ * supported.
+ */
+ bool return_nisv_io_abort_to_user;
};
#define KVM_NR_MEM_OBJS 40
@@ -235,6 +235,7 @@ struct kvm_hyperv_exit {
#define KVM_EXIT_S390_STSI 25
#define KVM_EXIT_IOAPIC_EOI 26
#define KVM_EXIT_HYPERV 27
+#define KVM_EXIT_ARM_NISV 28
/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@@ -394,6 +395,11 @@ struct kvm_run {
} eoi;
/* KVM_EXIT_HYPERV */
struct kvm_hyperv_exit hyperv;
+ /* KVM_EXIT_ARM_NISV */
+ struct {
+ __u64 esr_iss;
+ __u64 fault_ipa;
+ } arm_nisv;
/* Fix the size of the union. */
char padding[256];
};
@@ -1000,6 +1006,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_PMU_EVENT_FILTER 173
#define KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 174
#define KVM_CAP_HYPERV_DIRECT_TLBFLUSH 175
+#define KVM_CAP_ARM_NISV_TO_USER 176
#ifdef KVM_CAP_IRQ_ROUTING
@@ -98,6 +98,26 @@ int kvm_arch_check_processor_compat(void)
return 0;
}
+int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
+ struct kvm_enable_cap *cap)
+{
+ int r;
+
+ if (cap->flags)
+ return -EINVAL;
+
+ switch (cap->cap) {
+ case KVM_CAP_ARM_NISV_TO_USER:
+ r = 0;
+ kvm->arch.return_nisv_io_abort_to_user = true;
+ break;
+ default:
+ r = -EINVAL;
+ break;
+ }
+
+ return r;
+}
/**
* kvm_arch_init_vm - initializes a VM data structure
@@ -197,6 +217,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_IMMEDIATE_EXIT:
case KVM_CAP_VCPU_EVENTS:
case KVM_CAP_ARM_IRQ_LINE_LAYOUT_2:
+ case KVM_CAP_ARM_NISV_TO_USER:
r = 1;
break;
case KVM_CAP_ARM_SET_DEVICE_ADDR:
@@ -167,7 +167,14 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
if (ret)
return ret;
} else {
- kvm_err("load/store instruction decoding not implemented\n");
+ if (vcpu->kvm->arch.return_nisv_io_abort_to_user) {
+ run->exit_reason = KVM_EXIT_ARM_NISV;
+ run->arm_nisv.esr_iss = kvm_vcpu_dabt_iss_nisv_sanitized(vcpu);
+ run->arm_nisv.fault_ipa = fault_ipa;
+ return 0;
+ }
+
+ kvm_pr_unimpl("Data abort outside memslots with no valid syndrome info\n");
return -ENOSYS;
}