KVM: inject #UD if instruction emulation fails and exit to userspace
Do not kill VM when instruction emulation fails. Inject #UD and report
failure to userspace instead. Userspace may choose to reenter guest if
vcpu is in userspace (cpl == 3) in which case guest OS will kill
offending process and continue running.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fc5611b..ae9d6f3e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3639,24 +3639,6 @@
return __kvm_set_dr(vcpu, dr, value);
}
-void kvm_report_emulation_failure(struct kvm_vcpu *vcpu, const char *context)
-{
- u8 opcodes[4];
- unsigned long rip = kvm_rip_read(vcpu);
- unsigned long rip_linear;
-
- if (!printk_ratelimit())
- return;
-
- rip_linear = rip + get_segment_base(vcpu, VCPU_SREG_CS);
-
- kvm_read_guest_virt(rip_linear, (void *)opcodes, 4, vcpu, NULL);
-
- printk(KERN_ERR "emulation failed (%s) rip %lx %02x %02x %02x %02x\n",
- context, rip, opcodes[0], opcodes[1], opcodes[2], opcodes[3]);
-}
-EXPORT_SYMBOL_GPL(kvm_report_emulation_failure);
-
static u64 mk_cr_64(u64 curr_cr, u32 new_val)
{
return (curr_cr & ~((1ULL << 32) - 1)) | new_val;
@@ -3863,6 +3845,19 @@
kvm_queue_exception(vcpu, ctxt->exception);
}
+static int handle_emulation_failure(struct kvm_vcpu *vcpu)
+{
+ struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
+
+ ++vcpu->stat.insn_emulation_fail;
+ trace_kvm_emulate_insn_failed(vcpu);
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+ vcpu->run->internal.ndata = 0;
+ kvm_queue_exception(vcpu, UD_VECTOR);
+ return EMULATE_FAIL;
+}
+
int emulate_instruction(struct kvm_vcpu *vcpu,
unsigned long cr2,
u16 error_code,
@@ -3931,11 +3926,11 @@
++vcpu->stat.insn_emulation;
if (r) {
- ++vcpu->stat.insn_emulation_fail;
- trace_kvm_emulate_insn_failed(vcpu);
if (kvm_mmu_unprotect_page_virt(vcpu, cr2))
return EMULATE_DONE;
- return EMULATE_FAIL;
+ if (emulation_type & EMULTYPE_SKIP)
+ return EMULATE_FAIL;
+ return handle_emulation_failure(vcpu);
}
}
@@ -3960,9 +3955,7 @@
if (kvm_mmu_unprotect_page_virt(vcpu, cr2))
return EMULATE_DONE;
- trace_kvm_emulate_insn_failed(vcpu);
- kvm_report_emulation_failure(vcpu, "mmio");
- return EMULATE_FAIL;
+ return handle_emulation_failure(vcpu);
}
toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
@@ -4798,7 +4791,7 @@
vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
r = emulate_instruction(vcpu, 0, 0, EMULTYPE_NO_DECODE);
srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
- if (r == EMULATE_DO_MMIO) {
+ if (r != EMULATE_DONE) {
r = 0;
goto out;
}