Unlike VMCALL, the instructions VMXOFF, VMLAUNCH and VMRESUME should cause a UD
exception in real-mode or vm86. However, the emulator considers all these
instructions the same for the matter of mode checks, and emulation upon exit
due to #UD exception.
As a result, the hypervisor behaves incorrectly on vm86 mode. VMXOFF, VMLAUNCH
or VMRESUME cause on vm86 exit due to #UD. The hypervisor then emulates these
instruction and inject #GP to the guest instead of #UD.
This patch creates a new group for these instructions and mark only VMCALL as
an instruction which can be emulated.
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index e5bf130..a240fac 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3139,12 +3139,8 @@ static int em_clts(struct x86_emulate_ctxt *ctxt)
static int em_vmcall(struct x86_emulate_ctxt *ctxt)
{
- int rc;
-
- if (ctxt->modrm_mod != 3 || ctxt->modrm_rm != 1)
- return X86EMUL_UNHANDLEABLE;
+ int rc = ctxt->ops->fix_hypercall(ctxt);
- rc = ctxt->ops->fix_hypercall(ctxt);
if (rc != X86EMUL_CONTINUE)
return rc;
@@ -3562,6 +3558,12 @@ static int check_perm_out(struct x86_emulate_ctxt *ctxt)
F2bv(((_f) | DstReg | SrcMem | ModRM) & ~Lock, _e), \
F2bv(((_f) & ~Lock) | DstAcc | SrcImm, _e)
+static const struct opcode group7_rm0[] = {
+ N,
+ I(SrcNone | Priv | EmulateOnUD, em_vmcall),
+ N, N, N, N, N, N,
+};
+
static const struct opcode group7_rm1[] = {
DI(SrcNone | Priv, monitor),
DI(SrcNone | Priv, mwait),
@@ -3655,7 +3657,7 @@ static const struct group_dual group7 = { {
II(SrcMem16 | Mov | Priv, em_lmsw, lmsw),
II(SrcMem | ByteOp | Priv | NoAccess, em_invlpg, invlpg),
}, {
- I(SrcNone | Priv | EmulateOnUD, em_vmcall),
+ EXT(0, group7_rm0),
EXT(0, group7_rm1),
N, EXT(0, group7_rm3),
II(SrcNone | DstMem | Mov, em_smsw, smsw), N,
--
1.9.1
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