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Commit 6d77dbfc authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
Browse files

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: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 57bc24cf

arch/x86/include/asm/kvm_host.h

+0 −1
Original line number Diff line number Diff line
@@ -576,7 +576,6 @@ enum emulation_result { 
#define EMULTYPE_SKIP		    (1 << 2)

int emulate_instruction(struct kvm_vcpu *vcpu,

			unsigned long cr2, u16 error_code, int emulation_type);

void kvm_report_emulation_failure(struct kvm_vcpu *cvpu, const char *context);

void realmode_lgdt(struct kvm_vcpu *vcpu, u16 size, unsigned long address);

void realmode_lidt(struct kvm_vcpu *vcpu, u16 size, unsigned long address);

arch/x86/kvm/mmu.c

+1 −4
Original line number Diff line number Diff line
@@ -2814,11 +2814,8 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code) 
		return 1;

	case EMULATE_DO_MMIO:

		++vcpu->stat.mmio_exits;

		return 0;

		/* fall through */

	case EMULATE_FAIL:

		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;

		vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;

		vcpu->run->internal.ndata = 0;

		return 0;

	default:

		BUG();

arch/x86/kvm/svm.c

+3 −7
Original line number Diff line number Diff line
@@ -1535,7 +1535,7 @@ static int io_interception(struct vcpu_svm *svm) 
	string = (io_info & SVM_IOIO_STR_MASK) != 0;

	in = (io_info & SVM_IOIO_TYPE_MASK) != 0;

	if (string || in)

		return !(emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DO_MMIO);

		return emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DONE;



	port = io_info >> 16;

	size = (io_info & SVM_IOIO_SIZE_MASK) >> SVM_IOIO_SIZE_SHIFT;
@@ -2386,16 +2386,12 @@ static int iret_interception(struct vcpu_svm *svm) 


static int invlpg_interception(struct vcpu_svm *svm)

{

	if (emulate_instruction(&svm->vcpu, 0, 0, 0) != EMULATE_DONE)

		pr_unimpl(&svm->vcpu, "%s: failed\n", __func__);

	return 1;

	return emulate_instruction(&svm->vcpu, 0, 0, 0) == EMULATE_DONE;

}



static int emulate_on_interception(struct vcpu_svm *svm)

{

	if (emulate_instruction(&svm->vcpu, 0, 0, 0) != EMULATE_DONE)

		pr_unimpl(&svm->vcpu, "%s: failed\n", __func__);

	return 1;

	return emulate_instruction(&svm->vcpu, 0, 0, 0) == EMULATE_DONE;

}



static int cr8_write_interception(struct vcpu_svm *svm)

arch/x86/kvm/vmx.c

+4 −24
Original line number Diff line number Diff line
@@ -3070,7 +3070,7 @@ static int handle_io(struct kvm_vcpu *vcpu) 
	++vcpu->stat.io_exits;



	if (string || in)

		return !(emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DO_MMIO);

		return emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DONE;



	port = exit_qualification >> 16;

	size = (exit_qualification & 7) + 1;
@@ -3327,22 +3327,7 @@ static int handle_wbinvd(struct kvm_vcpu *vcpu) 


static int handle_apic_access(struct kvm_vcpu *vcpu)

{

	unsigned long exit_qualification;

	enum emulation_result er;

	unsigned long offset;



	exit_qualification = vmcs_readl(EXIT_QUALIFICATION);

	offset = exit_qualification & 0xffful;



	er = emulate_instruction(vcpu, 0, 0, 0);



	if (er !=  EMULATE_DONE) {

		printk(KERN_ERR

		       "Fail to handle apic access vmexit! Offset is 0x%lx\n",

		       offset);

		return -ENOEXEC;

	}

	return 1;

	return emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DONE;

}



static int handle_task_switch(struct kvm_vcpu *vcpu)
@@ -3554,13 +3539,8 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu) 
			goto out;

		}



		if (err != EMULATE_DONE) {

			vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;

			vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;

			vcpu->run->internal.ndata = 0;

			ret = 0;

			goto out;

		}

		if (err != EMULATE_DONE)

			return 0;



		if (signal_pending(current))

			goto out;

arch/x86/kvm/x86.c

+18 −25
Original line number Diff line number Diff line
@@ -3639,24 +3639,6 @@ int emulator_set_dr(int dr, unsigned long value, struct kvm_vcpu *vcpu) 
	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 @@ static void inject_emulated_exception(struct kvm_vcpu *vcpu) 
		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 @@ int emulate_instruction(struct kvm_vcpu *vcpu, 


		++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;

			if (emulation_type & EMULTYPE_SKIP)

				return EMULATE_FAIL;

			return handle_emulation_failure(vcpu);

		}

	}
@@ -3960,9 +3955,7 @@ restart: 
		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 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) 
		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;

		}