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?
Paolo
> ---
> 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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