KVM: Use task switch from emulator.c

Remove old task switch code from x86.c
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/emulate.c

@@ -2291,6 +2291,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
 	u16 old_tss_sel = ops->get_segment_selector(VCPU_SREG_TR, ctxt->vcpu);
 	ulong old_tss_base =
 		get_cached_descriptor_base(ctxt, ops, VCPU_SREG_TR);
+	u32 desc_limit;
 
 	/* FIXME: old_tss_base == ~0 ? */
 
@@ -2311,7 +2312,10 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
 		}
 	}
 
-	if (!next_tss_desc.p || desc_limit_scaled(&next_tss_desc) < 0x67) {
+	desc_limit = desc_limit_scaled(&next_tss_desc);
+	if (!next_tss_desc.p ||
+	    ((desc_limit < 0x67 && (next_tss_desc.type & 8)) ||
+	     desc_limit < 0x2b)) {
 		kvm_queue_exception_e(ctxt->vcpu, TS_VECTOR,
 				      tss_selector & 0xfffc);
 		return X86EMUL_PROPAGATE_FAULT;

arch/x86/kvm/x86.c

@@ -4832,557 +4832,30 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-static void seg_desct_to_kvm_desct(struct desc_struct *seg_desc, u16 selector,
-				   struct kvm_segment *kvm_desct)
-{
-	kvm_desct->base = get_desc_base(seg_desc);
-	kvm_desct->limit = get_desc_limit(seg_desc);
-	if (seg_desc->g) {
-		kvm_desct->limit <<= 12;
-		kvm_desct->limit |= 0xfff;
-	}
-	kvm_desct->selector = selector;
-	kvm_desct->type = seg_desc->type;
-	kvm_desct->present = seg_desc->p;
-	kvm_desct->dpl = seg_desc->dpl;
-	kvm_desct->db = seg_desc->d;
-	kvm_desct->s = seg_desc->s;
-	kvm_desct->l = seg_desc->l;
-	kvm_desct->g = seg_desc->g;
-	kvm_desct->avl = seg_desc->avl;
-	if (!selector)
-		kvm_desct->unusable = 1;
-	else
-		kvm_desct->unusable = 0;
-	kvm_desct->padding = 0;
-}
-
-static void get_segment_descriptor_dtable(struct kvm_vcpu *vcpu,
-					  u16 selector,
-					  struct desc_ptr *dtable)
-{
-	if (selector & 1 << 2) {
-		struct kvm_segment kvm_seg;
-
-		kvm_get_segment(vcpu, &kvm_seg, VCPU_SREG_LDTR);
-
-		if (kvm_seg.unusable)
-			dtable->size = 0;
-		else
-			dtable->size = kvm_seg.limit;
-		dtable->address = kvm_seg.base;
-	}
-	else
-		kvm_x86_ops->get_gdt(vcpu, dtable);
-}
-
-/* allowed just for 8 bytes segments */
-static int load_guest_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
-					 struct desc_struct *seg_desc)
-{
-	struct desc_ptr dtable;
-	u16 index = selector >> 3;
-	int ret;
-	u32 err;
-	gva_t addr;
-
-	get_segment_descriptor_dtable(vcpu, selector, &dtable);
-
-	if (dtable.size < index * 8 + 7) {
-		kvm_queue_exception_e(vcpu, GP_VECTOR, selector & 0xfffc);
-		return X86EMUL_PROPAGATE_FAULT;
-	}
-	addr = dtable.base + index * 8;
-	ret = kvm_read_guest_virt_system(addr, seg_desc, sizeof(*seg_desc),
-					 vcpu,  &err);
-	if (ret == X86EMUL_PROPAGATE_FAULT)
-		kvm_inject_page_fault(vcpu, addr, err);
-
-       return ret;
-}
-
-/* allowed just for 8 bytes segments */
-static int save_guest_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
-					 struct desc_struct *seg_desc)
-{
-	struct desc_ptr dtable;
-	u16 index = selector >> 3;
-
-	get_segment_descriptor_dtable(vcpu, selector, &dtable);
-
-	if (dtable.size < index * 8 + 7)
-		return 1;
-	return kvm_write_guest_virt(dtable.address + index*8, seg_desc, sizeof(*seg_desc), vcpu, NULL);
-}
-
-static gpa_t get_tss_base_addr_write(struct kvm_vcpu *vcpu,
-			       struct desc_struct *seg_desc)
-{
-	u32 base_addr = get_desc_base(seg_desc);
-
-	return kvm_mmu_gva_to_gpa_write(vcpu, base_addr, NULL);
-}
-
-static gpa_t get_tss_base_addr_read(struct kvm_vcpu *vcpu,
-			     struct desc_struct *seg_desc)
-{
-	u32 base_addr = get_desc_base(seg_desc);
-
-	return kvm_mmu_gva_to_gpa_read(vcpu, base_addr, NULL);
-}
-
-static u16 get_segment_selector(struct kvm_vcpu *vcpu, int seg)
-{
-	struct kvm_segment kvm_seg;
-
-	kvm_get_segment(vcpu, &kvm_seg, seg);
-	return kvm_seg.selector;
-}
-
-static int kvm_load_realmode_segment(struct kvm_vcpu *vcpu, u16 selector, int seg)
-{
-	struct kvm_segment segvar = {
-		.base = selector << 4,
-		.limit = 0xffff,
-		.selector = selector,
-		.type = 3,
-		.present = 1,
-		.dpl = 3,
-		.db = 0,
-		.s = 1,
-		.l = 0,
-		.g = 0,
-		.avl = 0,
-		.unusable = 0,
-	};
-	kvm_x86_ops->set_segment(vcpu, &segvar, seg);
-	return X86EMUL_CONTINUE;
-}
-
-static int is_vm86_segment(struct kvm_vcpu *vcpu, int seg)
-{
-	return (seg != VCPU_SREG_LDTR) &&
-		(seg != VCPU_SREG_TR) &&
-		(kvm_get_rflags(vcpu) & X86_EFLAGS_VM);
-}
-
-int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector, int seg)
-{
-	struct kvm_segment kvm_seg;
-	struct desc_struct seg_desc;
-	u8 dpl, rpl, cpl;
-	unsigned err_vec = GP_VECTOR;
-	u32 err_code = 0;
-	bool null_selector = !(selector & ~0x3); /* 0000-0003 are null */
-	int ret;
-
-	if (is_vm86_segment(vcpu, seg) || !is_protmode(vcpu))
-		return kvm_load_realmode_segment(vcpu, selector, seg);
-
-	/* NULL selector is not valid for TR, CS and SS */
-	if ((seg == VCPU_SREG_CS || seg == VCPU_SREG_SS || seg == VCPU_SREG_TR)
-	    && null_selector)
-		goto exception;
-
-	/* TR should be in GDT only */
-	if (seg == VCPU_SREG_TR && (selector & (1 << 2)))
-		goto exception;
-
-	ret = load_guest_segment_descriptor(vcpu, selector, &seg_desc);
-	if (ret)
-		return ret;
-
-	seg_desct_to_kvm_desct(&seg_desc, selector, &kvm_seg);
-
-	if (null_selector) { /* for NULL selector skip all following checks */
-		kvm_seg.unusable = 1;
-		goto load;
-	}
-
-	err_code = selector & 0xfffc;
-	err_vec = GP_VECTOR;
-
-	/* can't load system descriptor into segment selecor */
-	if (seg <= VCPU_SREG_GS && !kvm_seg.s)
-		goto exception;
-
-	if (!kvm_seg.present) {
-		err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;
-		goto exception;
-	}
-
-	rpl = selector & 3;
-	dpl = kvm_seg.dpl;
-	cpl = kvm_x86_ops->get_cpl(vcpu);
-
-	switch (seg) {
-	case VCPU_SREG_SS:
-		/*
-		 * segment is not a writable data segment or segment
-		 * selector's RPL != CPL or segment selector's RPL != CPL
-		 */
-		if (rpl != cpl || (kvm_seg.type & 0xa) != 0x2 || dpl != cpl)
-			goto exception;
-		break;
-	case VCPU_SREG_CS:
-		if (!(kvm_seg.type & 8))
-			goto exception;
-
-		if (kvm_seg.type & 4) {
-			/* conforming */
-			if (dpl > cpl)
-				goto exception;
-		} else {
-			/* nonconforming */
-			if (rpl > cpl || dpl != cpl)
-				goto exception;
-		}
-		/* CS(RPL) <- CPL */
-		selector = (selector & 0xfffc) | cpl;
-            break;
-	case VCPU_SREG_TR:
-		if (kvm_seg.s || (kvm_seg.type != 1 && kvm_seg.type != 9))
-			goto exception;
-		break;
-	case VCPU_SREG_LDTR:
-		if (kvm_seg.s || kvm_seg.type != 2)
-			goto exception;
-		break;
-	default: /*  DS, ES, FS, or GS */
-		/*
-		 * segment is not a data or readable code segment or
-		 * ((segment is a data or nonconforming code segment)
-		 * and (both RPL and CPL > DPL))
-		 */
-		if ((kvm_seg.type & 0xa) == 0x8 ||
-		    (((kvm_seg.type & 0xc) != 0xc) && (rpl > dpl && cpl > dpl)))
-			goto exception;
-		break;
-	}
-
-	if (!kvm_seg.unusable && kvm_seg.s) {
-		/* mark segment as accessed */
-		kvm_seg.type |= 1;
-		seg_desc.type |= 1;
-		save_guest_segment_descriptor(vcpu, selector, &seg_desc);
-	}
-load:
-	kvm_set_segment(vcpu, &kvm_seg, seg);
-	return X86EMUL_CONTINUE;
-exception:
-	kvm_queue_exception_e(vcpu, err_vec, err_code);
-	return X86EMUL_PROPAGATE_FAULT;
-}
-
-static void save_state_to_tss32(struct kvm_vcpu *vcpu,
-				struct tss_segment_32 *tss)
-{
-	tss->cr3 = vcpu->arch.cr3;
-	tss->eip = kvm_rip_read(vcpu);
-	tss->eflags = kvm_get_rflags(vcpu);
-	tss->eax = kvm_register_read(vcpu, VCPU_REGS_RAX);
-	tss->ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
-	tss->edx = kvm_register_read(vcpu, VCPU_REGS_RDX);
-	tss->ebx = kvm_register_read(vcpu, VCPU_REGS_RBX);
-	tss->esp = kvm_register_read(vcpu, VCPU_REGS_RSP);
-	tss->ebp = kvm_register_read(vcpu, VCPU_REGS_RBP);
-	tss->esi = kvm_register_read(vcpu, VCPU_REGS_RSI);
-	tss->edi = kvm_register_read(vcpu, VCPU_REGS_RDI);
-	tss->es = get_segment_selector(vcpu, VCPU_SREG_ES);
-	tss->cs = get_segment_selector(vcpu, VCPU_SREG_CS);
-	tss->ss = get_segment_selector(vcpu, VCPU_SREG_SS);
-	tss->ds = get_segment_selector(vcpu, VCPU_SREG_DS);
-	tss->fs = get_segment_selector(vcpu, VCPU_SREG_FS);
-	tss->gs = get_segment_selector(vcpu, VCPU_SREG_GS);
-	tss->ldt_selector = get_segment_selector(vcpu, VCPU_SREG_LDTR);
-}
-
-static void kvm_load_segment_selector(struct kvm_vcpu *vcpu, u16 sel, int seg)
-{
-	struct kvm_segment kvm_seg;
-	kvm_get_segment(vcpu, &kvm_seg, seg);
-	kvm_seg.selector = sel;
-	kvm_set_segment(vcpu, &kvm_seg, seg);
-}
-
-static int load_state_from_tss32(struct kvm_vcpu *vcpu,
-				  struct tss_segment_32 *tss)
-{
-	kvm_set_cr3(vcpu, tss->cr3);
-
-	kvm_rip_write(vcpu, tss->eip);
-	kvm_set_rflags(vcpu, tss->eflags | 2);
-
-	kvm_register_write(vcpu, VCPU_REGS_RAX, tss->eax);
-	kvm_register_write(vcpu, VCPU_REGS_RCX, tss->ecx);
-	kvm_register_write(vcpu, VCPU_REGS_RDX, tss->edx);
-	kvm_register_write(vcpu, VCPU_REGS_RBX, tss->ebx);
-	kvm_register_write(vcpu, VCPU_REGS_RSP, tss->esp);
-	kvm_register_write(vcpu, VCPU_REGS_RBP, tss->ebp);
-	kvm_register_write(vcpu, VCPU_REGS_RSI, tss->esi);
-	kvm_register_write(vcpu, VCPU_REGS_RDI, tss->edi);
-
-	/*
-	 * SDM says that segment selectors are loaded before segment
-	 * descriptors
-	 */
-	kvm_load_segment_selector(vcpu, tss->ldt_selector, VCPU_SREG_LDTR);
-	kvm_load_segment_selector(vcpu, tss->es, VCPU_SREG_ES);
-	kvm_load_segment_selector(vcpu, tss->cs, VCPU_SREG_CS);
-	kvm_load_segment_selector(vcpu, tss->ss, VCPU_SREG_SS);
-	kvm_load_segment_selector(vcpu, tss->ds, VCPU_SREG_DS);
-	kvm_load_segment_selector(vcpu, tss->fs, VCPU_SREG_FS);
-	kvm_load_segment_selector(vcpu, tss->gs, VCPU_SREG_GS);
-
-	/*
-	 * Now load segment descriptors. If fault happenes at this stage
-	 * it is handled in a context of new task
-	 */
-	if (kvm_load_segment_descriptor(vcpu, tss->ldt_selector, VCPU_SREG_LDTR))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->es, VCPU_SREG_ES))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->cs, VCPU_SREG_CS))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->ss, VCPU_SREG_SS))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->ds, VCPU_SREG_DS))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->fs, VCPU_SREG_FS))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->gs, VCPU_SREG_GS))
-		return 1;
-	return 0;
-}
-
-static void save_state_to_tss16(struct kvm_vcpu *vcpu,
-				struct tss_segment_16 *tss)
-{
-	tss->ip = kvm_rip_read(vcpu);
-	tss->flag = kvm_get_rflags(vcpu);
-	tss->ax = kvm_register_read(vcpu, VCPU_REGS_RAX);
-	tss->cx = kvm_register_read(vcpu, VCPU_REGS_RCX);
-	tss->dx = kvm_register_read(vcpu, VCPU_REGS_RDX);
-	tss->bx = kvm_register_read(vcpu, VCPU_REGS_RBX);
-	tss->sp = kvm_register_read(vcpu, VCPU_REGS_RSP);
-	tss->bp = kvm_register_read(vcpu, VCPU_REGS_RBP);
-	tss->si = kvm_register_read(vcpu, VCPU_REGS_RSI);
-	tss->di = kvm_register_read(vcpu, VCPU_REGS_RDI);
-
-	tss->es = get_segment_selector(vcpu, VCPU_SREG_ES);
-	tss->cs = get_segment_selector(vcpu, VCPU_SREG_CS);
-	tss->ss = get_segment_selector(vcpu, VCPU_SREG_SS);
-	tss->ds = get_segment_selector(vcpu, VCPU_SREG_DS);
-	tss->ldt = get_segment_selector(vcpu, VCPU_SREG_LDTR);
-}
-
-static int load_state_from_tss16(struct kvm_vcpu *vcpu,
-				 struct tss_segment_16 *tss)
-{
-	kvm_rip_write(vcpu, tss->ip);
-	kvm_set_rflags(vcpu, tss->flag | 2);
-	kvm_register_write(vcpu, VCPU_REGS_RAX, tss->ax);
-	kvm_register_write(vcpu, VCPU_REGS_RCX, tss->cx);
-	kvm_register_write(vcpu, VCPU_REGS_RDX, tss->dx);
-	kvm_register_write(vcpu, VCPU_REGS_RBX, tss->bx);
-	kvm_register_write(vcpu, VCPU_REGS_RSP, tss->sp);
-	kvm_register_write(vcpu, VCPU_REGS_RBP, tss->bp);
-	kvm_register_write(vcpu, VCPU_REGS_RSI, tss->si);
-	kvm_register_write(vcpu, VCPU_REGS_RDI, tss->di);
-
-	/*
-	 * SDM says that segment selectors are loaded before segment
-	 * descriptors
-	 */
-	kvm_load_segment_selector(vcpu, tss->ldt, VCPU_SREG_LDTR);
-	kvm_load_segment_selector(vcpu, tss->es, VCPU_SREG_ES);
-	kvm_load_segment_selector(vcpu, tss->cs, VCPU_SREG_CS);
-	kvm_load_segment_selector(vcpu, tss->ss, VCPU_SREG_SS);
-	kvm_load_segment_selector(vcpu, tss->ds, VCPU_SREG_DS);
-
-	/*
-	 * Now load segment descriptors. If fault happenes at this stage
-	 * it is handled in a context of new task
-	 */
-	if (kvm_load_segment_descriptor(vcpu, tss->ldt, VCPU_SREG_LDTR))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->es, VCPU_SREG_ES))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->cs, VCPU_SREG_CS))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->ss, VCPU_SREG_SS))
-		return 1;
-
-	if (kvm_load_segment_descriptor(vcpu, tss->ds, VCPU_SREG_DS))
-		return 1;
-	return 0;
-}
-
-static int kvm_task_switch_16(struct kvm_vcpu *vcpu, u16 tss_selector,
-			      u16 old_tss_sel, u32 old_tss_base,
-			      struct desc_struct *nseg_desc)
-{
-	struct tss_segment_16 tss_segment_16;
-	int ret = 0;
-
-	if (kvm_read_guest(vcpu->kvm, old_tss_base, &tss_segment_16,
-			   sizeof tss_segment_16))
-		goto out;
-
-	save_state_to_tss16(vcpu, &tss_segment_16);
-
-	if (kvm_write_guest(vcpu->kvm, old_tss_base, &tss_segment_16,
-			    sizeof tss_segment_16))
-		goto out;
-
-	if (kvm_read_guest(vcpu->kvm, get_tss_base_addr_read(vcpu, nseg_desc),
-			   &tss_segment_16, sizeof tss_segment_16))
-		goto out;
-
-	if (old_tss_sel != 0xffff) {
-		tss_segment_16.prev_task_link = old_tss_sel;
-
-		if (kvm_write_guest(vcpu->kvm,
-				    get_tss_base_addr_write(vcpu, nseg_desc),
-				    &tss_segment_16.prev_task_link,
-				    sizeof tss_segment_16.prev_task_link))
-			goto out;
-	}
-
-	if (load_state_from_tss16(vcpu, &tss_segment_16))
-		goto out;
-
-	ret = 1;
-out:
-	return ret;
-}
-
-static int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16 tss_selector,
-		       u16 old_tss_sel, u32 old_tss_base,
-		       struct desc_struct *nseg_desc)
-{
-	struct tss_segment_32 tss_segment_32;
-	int ret = 0;
-
-	if (kvm_read_guest(vcpu->kvm, old_tss_base, &tss_segment_32,
-			   sizeof tss_segment_32))
-		goto out;
-
-	save_state_to_tss32(vcpu, &tss_segment_32);
-
-	if (kvm_write_guest(vcpu->kvm, old_tss_base, &tss_segment_32,
-			    sizeof tss_segment_32))
-		goto out;
-
-	if (kvm_read_guest(vcpu->kvm, get_tss_base_addr_read(vcpu, nseg_desc),
-			   &tss_segment_32, sizeof tss_segment_32))
-		goto out;
-
-	if (old_tss_sel != 0xffff) {
-		tss_segment_32.prev_task_link = old_tss_sel;
-
-		if (kvm_write_guest(vcpu->kvm,
-				    get_tss_base_addr_write(vcpu, nseg_desc),
-				    &tss_segment_32.prev_task_link,
-				    sizeof tss_segment_32.prev_task_link))
-			goto out;
-	}
-
-	if (load_state_from_tss32(vcpu, &tss_segment_32))
-		goto out;
-
-	ret = 1;
-out:
-	return ret;
-}
-
 int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason)
 {
-	struct kvm_segment tr_seg;
-	struct desc_struct cseg_desc;
-	struct desc_struct nseg_desc;
-	int ret = 0;
-	u32 old_tss_base = get_segment_base(vcpu, VCPU_SREG_TR);
-	u16 old_tss_sel = get_segment_selector(vcpu, VCPU_SREG_TR);
-	u32 desc_limit;
-
-	old_tss_base = kvm_mmu_gva_to_gpa_write(vcpu, old_tss_base, NULL);
-
-	/* FIXME: Handle errors. Failure to read either TSS or their
-	 * descriptors should generate a pagefault.
-	 */
-	if (load_guest_segment_descriptor(vcpu, tss_selector, &nseg_desc))
-		goto out;
-
-	if (load_guest_segment_descriptor(vcpu, old_tss_sel, &cseg_desc))
-		goto out;
-
-	if (reason != TASK_SWITCH_IRET) {
-		int cpl;
-
-		cpl = kvm_x86_ops->get_cpl(vcpu);
-		if ((tss_selector & 3) > nseg_desc.dpl || cpl > nseg_desc.dpl) {
-			kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
-			return 1;
-		}
-	}
-
-	desc_limit = get_desc_limit(&nseg_desc);
-	if (!nseg_desc.p ||
-	    ((desc_limit < 0x67 && (nseg_desc.type & 8)) ||
-	     desc_limit < 0x2b)) {
-		kvm_queue_exception_e(vcpu, TS_VECTOR, tss_selector & 0xfffc);
-		return 1;
-	}
-
-	if (reason == TASK_SWITCH_IRET || reason == TASK_SWITCH_JMP) {
-		cseg_desc.type &= ~(1 << 1); //clear the B flag
-		save_guest_segment_descriptor(vcpu, old_tss_sel, &cseg_desc);
-	}
-
-	if (reason == TASK_SWITCH_IRET) {
-		u32 eflags = kvm_get_rflags(vcpu);
-		kvm_set_rflags(vcpu, eflags & ~X86_EFLAGS_NT);
-	}
+	int cs_db, cs_l, ret;
+	cache_all_regs(vcpu);
 
-	/* set back link to prev task only if NT bit is set in eflags
-	   note that old_tss_sel is not used afetr this point */
-	if (reason != TASK_SWITCH_CALL && reason != TASK_SWITCH_GATE)
-		old_tss_sel = 0xffff;
+	kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
 
-	if (nseg_desc.type & 8)
-		ret = kvm_task_switch_32(vcpu, tss_selector, old_tss_sel,
-					 old_tss_base, &nseg_desc);
-	else
-		ret = kvm_task_switch_16(vcpu, tss_selector, old_tss_sel,
-					 old_tss_base, &nseg_desc);
+	vcpu->arch.emulate_ctxt.vcpu = vcpu;
+	vcpu->arch.emulate_ctxt.eflags = kvm_x86_ops->get_rflags(vcpu);
+	vcpu->arch.emulate_ctxt.eip = kvm_rip_read(vcpu);
+	vcpu->arch.emulate_ctxt.mode =
+		(!is_protmode(vcpu)) ? X86EMUL_MODE_REAL :
+		(vcpu->arch.emulate_ctxt.eflags & X86_EFLAGS_VM)
+		? X86EMUL_MODE_VM86 : cs_l
+		? X86EMUL_MODE_PROT64 :	cs_db
+		? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;
 
-	if (reason == TASK_SWITCH_CALL || reason == TASK_SWITCH_GATE) {
-		u32 eflags = kvm_get_rflags(vcpu);
-		kvm_set_rflags(vcpu, eflags | X86_EFLAGS_NT);
-	}
+	ret = emulator_task_switch(&vcpu->arch.emulate_ctxt, &emulate_ops,
+				   tss_selector, reason);
 
-	if (reason != TASK_SWITCH_IRET) {
-		nseg_desc.type |= (1 << 1);
-		save_guest_segment_descriptor(vcpu, tss_selector,
-					      &nseg_desc);
-	}
+	if (ret == X86EMUL_CONTINUE)
+		kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
 
-	kvm_x86_ops->set_cr0(vcpu, kvm_read_cr0(vcpu) | X86_CR0_TS);
-	seg_desct_to_kvm_desct(&nseg_desc, tss_selector, &tr_seg);
-	tr_seg.type = 11;
-	kvm_set_segment(vcpu, &tr_seg, VCPU_SREG_TR);
-out:
-	return ret;
+	return (ret != X86EMUL_CONTINUE);
 }
 EXPORT_SYMBOL_GPL(kvm_task_switch);