From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH 8/9] MIPS: KVM: Decode RDHWR more strictly
Date: Tue, 5 Jul 2016 14:51:12 +0200
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 <1467657315-19975-9-git-send-email-james.hogan@imgtec.com>
 <24b4b1b6-2a58-63f8-f2c2-78ecc6eceb4e@cogentembedded.com>
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Cc: James Hogan <james.hogan@imgtec.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Paul Burton <paul.burton@imgtec.com>,
        linux-mips@linux-mips.org, kvm@vger.kernel.org
To: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
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On Tue, Jul 05, 2016 at 02:16:48PM +0300, Sergei Shtylyov wrote:

> > When KVM emulates the RDHWR instruction, decode the instruction mor=
e
> > strictly. The rs field (bits 25:21) should be zero, as should bits =
10:9.
> > Bits 8:6 is the register select field in MIPSr6, so we aren't stric=
t
> > about those bits (no other operations should use that encoding spac=
e).
> >=20
> > Signed-off-by: James Hogan <james.hogan@imgtec.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Radim Kr=C4=8Dm=C3=A1=C5=99 <rkrcmar@redhat.com>
> > Cc: Ralf Baechle <ralf@linux-mips.org>
> > Cc: linux-mips@linux-mips.org
> > Cc: kvm@vger.kernel.org
> > ---
> >  arch/mips/kvm/emulate.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >=20
> > diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
> > index 62e6a7b313ae..be18dfe9ecaa 100644
> > --- a/arch/mips/kvm/emulate.c
> > +++ b/arch/mips/kvm/emulate.c
> > @@ -2357,7 +2357,9 @@ enum emulation_result kvm_mips_handle_ri(u32 =
cause, u32 *opc,
> >  	}
> >=20
> >  	if (inst.r_format.opcode =3D=3D spec3_op &&
> > -	    inst.r_format.func =3D=3D rdhwr_op) {
> > +	    inst.r_format.func =3D=3D rdhwr_op &&
> > +	    inst.r_format.rs =3D=3D 0 &&
> > +	    (inst.r_format.re >> 3) =3D=3D 0) {
>=20
>    Inner parens not necessary here.

While I often strip unnecessary parens from patches I apply my guidelin=
e for
leaving them in is that nobody should need to know all C operator prior=
ities
by heart.

  Ralf