On Aug 29, 2014, at 11:36 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> Il 29/08/2014 10:26, Nadav Amit ha scritto:
>> 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>
>
> Patch looks good, but where is the check that MOD == 3 in the "case
> RMExt"? Am I just not seeing it?
>
This seems to be part of the “case GroupDual”.
>> ---
>> 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,
>>
>
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