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Subject[PATCH 29/47] KVM: x86 emulator: Add sysenter emulation
Date
From: Andre Przywara <andre.przywara@amd.com>

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: Christoph Egger <christoph.egger@amd.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/x86_emulate.c | 70 +++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 69 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 4d7256d..7a9bddb 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -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 @@ twobyte_insn:
c->dst.type = OP_NONE;
break;
case 0x34: /* sysenter */
- goto cannot_emulate;
+ if (emulate_sysenter(ctxt) == -1)
+ goto cannot_emulate;
+ else
+ goto writeback;
break;
case 0x35: /* sysexit */
goto cannot_emulate;
--
1.6.3.3


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