Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20190501202830.347656894@goodmis.org> <20190501203152.397154664@goodmis.org>
 <20190501232412.1196ef18@oasis.local.home> <20190502162133.GX2623@hirez.programming.kicks-ass.net>
 <CAHk-=wijZ-MD4g3zMJ9W2r=h8LUWneiu29OWuxZEoSfAF=0bhQ@mail.gmail.com>
 <20190502181811.GY2623@hirez.programming.kicks-ass.net> <CAHk-=wi6A9tgw=kkPh5Ywqt687VvsVEjYXVkAnq0jpt0u0tk6g@mail.gmail.com>
 <20190502202146.GZ2623@hirez.programming.kicks-ass.net> <CAHk-=wh8bi5c_GkyjPtDAiaXaZRqtmhWs30usUvs4qK_F+c9tg@mail.gmail.com>
 <20190503152405.2d741af8@gandalf.local.home> <CAHk-=wiA-WbrFrDs-kOfJZMXy4zMo9-SZfk=7B-GfmBJ866naw@mail.gmail.com>
 <20190503184919.2b7ef242@gandalf.local.home> <CAHk-=wh2vPLvsGBi6JtmEYeqHxB5UpTzHDjY5JsWG=YR0Lypzw@mail.gmail.com>
 <20190504001756.17fad840@oasis.local.home> <CAHk-=wiuSFbv_rELND-BLWcP0GSZ0yF=xOAEcf61GE3bU9d=yg@mail.gmail.com>
 <CAHk-=wjGNx8xcwg=7nE_0-nLQ_d4UALHvJ8O+TurbA25n8MyNg@mail.gmail.com> <2BF1AE4B-8105-49F0-8B6A-AA3B11FD66FD@amacapital.net>
In-Reply-To: <2BF1AE4B-8105-49F0-8B6A-AA3B11FD66FD@amacapital.net>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 4 May 2019 13:36:11 -0700
Message-ID: <CAHk-=wgEDAFUKRR=iELwUCk1kpoACk4eOfyyQhnYb78H9AEaSw@mail.gmail.com>
Subject: Re: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions
To:     Andy Lutomirski <luto@amacapital.net>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Nicolai Stange <nstange@suse.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jiri Kosina <jikos@kernel.org>,
        Miroslav Benes <mbenes@suse.cz>,
        Petr Mladek <pmladek@suse.com>,
        Joe Lawrence <joe.lawrence@redhat.com>,
        Shuah Khan <shuah@kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Juergen Gross <jgross@suse.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nayna Jain <nayna@linux.ibm.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Joerg Roedel <jroedel@suse.de>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>, stable <stable@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sat, May 4, 2019 at 1:12 PM Andy Lutomirski <luto@amacapital.net> wrote:
>
> As an aside, is it even *possible* to get #BP from v8086 mode?  On a quic=
k SDM read, the INT3 instruction causes #GP if VM=3D1 and IOPL<3.  And, if =
we allow vm86() to have IOPL=3D3, we should just remove that ability. It=E2=
=80=99s nuts.

Oh, and I think you mis-read the SDM.

Yes, iopl matters for "int X" (cd xx) instruction in vm86 mode.

But no, iopl does *not* matter for the special "int3/into/int1"
(cc/ce/f1) instructions, I think.

              Linus