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From:   Jan Dakinevich <jan.dakinevich@virtuozzo.com>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Denis Lunev <den@virtuozzo.com>,
        Roman Kagan <rkagan@virtuozzo.com>,
        Denis Plotnikov <dplotnikov@virtuozzo.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        =?iso-8859-2?Q?Radim_Kr=E8m=E1=F8?= <rkrcmar@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH 2/3] KVM: x86: set ctxt->have_exception in
 x86_decode_insn()
Thread-Topic: [PATCH 2/3] KVM: x86: set ctxt->have_exception in
 x86_decode_insn()
Thread-Index: AQHVXNhUGXqiO0HWykadKGZM7EVsb6cPFNEAgAFFooA=
Date:   Wed, 28 Aug 2019 10:19:30 +0000
Message-ID: <20190828131927.8be518098e0690f6e8d39f0c@virtuozzo.com>
References: <1566911210-30059-1-git-send-email-jan.dakinevich@virtuozzo.com>
        <1566911210-30059-3-git-send-email-jan.dakinevich@virtuozzo.com>
        <20190827145358.GD27459@linux.intel.com>
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On Tue, 27 Aug 2019 07:53:58 -0700
Sean Christopherson <sean.j.christopherson@intel.com> wrote:

> On Tue, Aug 27, 2019 at 01:07:08PM +0000, Jan Dakinevich wrote:
> > x86_emulate_instruction() takes into account ctxt->have_exception flag
> > during instruction decoding, but in practice this flag is never set in
> > x86_decode_insn().
> >=20
> > Fixes: 6ea6e84 ("KVM: x86: inject exceptions produced by x86_decode_ins=
n")
> > Cc: Denis Lunev <den@virtuozzo.com>
> > Cc: Roman Kagan <rkagan@virtuozzo.com>
> > Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
> > Signed-off-by: Jan Dakinevich <jan.dakinevich@virtuozzo.com>
> > ---
> >  arch/x86/kvm/emulate.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >=20
> > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > index 6170ddf..f93880f 100644
> > --- a/arch/x86/kvm/emulate.c
> > +++ b/arch/x86/kvm/emulate.c
> > @@ -5395,6 +5395,8 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt=
, void *insn, int insn_len)
> >  					ctxt->memopp->addr.mem.ea + ctxt->_eip);
> > =20
> >  done:
> > +	if (rc =3D=3D X86EMUL_PROPAGATE_FAULT)
> > +		ctxt->have_exception =3D true;
>=20
> We should add a sanity check or two on the vector since the emulator code
> goes all over the place, e.g. #UD should not be injected/propagated, and
> trap-like exceptions should not be handled/encountered during decode.
> Note, exception_type() also warns on illegal vectors.
>=20
>   WARN_ON_ONCE(ctxt->exception.vector =3D=3D UD_VECTOR ||
> 	       exception_type(ctxt->exception.vector) =3D=3D EXCPT_TRAP);

Ok.

>=20
> >  	return (rc !=3D X86EMUL_CONTINUE) ? EMULATION_FAILED : EMULATION_OK;
> >  }
> > =20
> > --=20
> > 2.1.4
> >=20


--=20
Best regards
Jan Dakinevich