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Commit 8c604352 authored by Andre Przywara's avatar Andre Przywara Committed by Avi Kivity
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KVM: x86 emulator: Add sysenter emulation 



Handle #UD intercept of the sysenter instruction in 32bit compat mode on
an AMD host.
Setup the segment descriptors for CS and SS and the EIP/ESP registers
according to the manual.

Signed-off-by: default avatarChristoph Egger <christoph.egger@amd.com>
Signed-off-by: default avatarAmit Shah <amit.shah@redhat.com>
Signed-off-by: default avatarAndre Przywara <andre.przywara@amd.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent e66bb2cc

arch/x86/kvm/x86_emulate.c

+69 −1
Original line number Diff line number Diff line
@@ -1476,6 +1476,71 @@ emulate_syscall(struct x86_emulate_ctxt *ctxt) 
	return 0;

}



static int

emulate_sysenter(struct x86_emulate_ctxt *ctxt)

{

	struct decode_cache *c = &ctxt->decode;

	struct kvm_segment cs, ss;

	u64 msr_data;



	/* inject #UD if LOCK prefix is used */

	if (c->lock_prefix)

		return -1;



	/* inject #GP if in real mode or paging is disabled */

	if (ctxt->mode == X86EMUL_MODE_REAL ||

		!(ctxt->vcpu->arch.cr0 & X86_CR0_PE)) {

		kvm_inject_gp(ctxt->vcpu, 0);

		return -1;

	}



	/* XXX sysenter/sysexit have not been tested in 64bit mode.

	* Therefore, we inject an #UD.

	*/

	if (ctxt->mode == X86EMUL_MODE_PROT64)

		return -1;



	setup_syscalls_segments(ctxt, &cs, &ss);



	kvm_x86_ops->get_msr(ctxt->vcpu, MSR_IA32_SYSENTER_CS, &msr_data);

	switch (ctxt->mode) {

	case X86EMUL_MODE_PROT32:

		if ((msr_data & 0xfffc) == 0x0) {

			kvm_inject_gp(ctxt->vcpu, 0);

			return -1;

		}

		break;

	case X86EMUL_MODE_PROT64:

		if (msr_data == 0x0) {

			kvm_inject_gp(ctxt->vcpu, 0);

			return -1;

		}

		break;

	}



	ctxt->eflags &= ~(EFLG_VM | EFLG_IF | EFLG_RF);

	cs.selector = (u16)msr_data;

	cs.selector &= ~SELECTOR_RPL_MASK;

	ss.selector = cs.selector + 8;

	ss.selector &= ~SELECTOR_RPL_MASK;

	if (ctxt->mode == X86EMUL_MODE_PROT64

		|| is_long_mode(ctxt->vcpu)) {

		cs.db = 0;

		cs.l = 1;

	}



	kvm_x86_ops->set_segment(ctxt->vcpu, &cs, VCPU_SREG_CS);

	kvm_x86_ops->set_segment(ctxt->vcpu, &ss, VCPU_SREG_SS);



	kvm_x86_ops->get_msr(ctxt->vcpu, MSR_IA32_SYSENTER_EIP, &msr_data);

	c->eip = msr_data;



	kvm_x86_ops->get_msr(ctxt->vcpu, MSR_IA32_SYSENTER_ESP, &msr_data);

	c->regs[VCPU_REGS_RSP] = msr_data;



	return 0;

}



int

x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)

{
@@ -2144,7 +2209,10 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
		c->dst.type = OP_NONE;

		break;

	case 0x34:		/* sysenter */

		if (emulate_sysenter(ctxt) == -1)

			goto cannot_emulate;

		else

			goto writeback;

		break;

	case 0x35:		/* sysexit */

		goto cannot_emulate;