Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 1 Aug 2023 20:12:55 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Josh Poimboeuf <jpoimboe@kernel.org>
Cc:     Valentin Schneider <vschneid@redhat.com>,
        linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org,
        bpf@vger.kernel.org, x86@kernel.org, rcu@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Neeraj Upadhyay <quic_neeraju@quicinc.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Zqiang <qiang.zhang1211@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Uladzislau Rezki <urezki@gmail.com>,
        Christoph Hellwig <hch@infradead.org>,
        Lorenzo Stoakes <lstoakes@gmail.com>,
        Jason Baron <jbaron@akamai.com>,
        Kees Cook <keescook@chromium.org>,
        Sami Tolvanen <samitolvanen@google.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Juerg Haefliger <juerg.haefliger@canonical.com>,
        Nicolas Saenz Julienne <nsaenz@kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Nadav Amit <namit@vmware.com>,
        Dan Carpenter <error27@gmail.com>,
        Chuang Wang <nashuiliang@gmail.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Petr Mladek <pmladek@suse.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>, Song Liu <song@kernel.org>,
        Julian Pidancet <julian.pidancet@oracle.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Dionna Glaze <dionnaglaze@google.com>,
        Thomas =?iso-8859-1?Q?Wei=DFschuh?= <linux@weissschuh.net>,
        Juri Lelli <juri.lelli@redhat.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        Yair Podemsky <ypodemsk@redhat.com>
Subject: Re: [RFC PATCH v2 11/20] objtool: Flesh out warning related to
 pv_ops[] calls
Message-ID: <20230801181255.GE11704@hirez.programming.kicks-ass.net>
References: <20230720163056.2564824-1-vschneid@redhat.com>
 <20230720163056.2564824-12-vschneid@redhat.com>
 <20230728153334.myvh5sxppvjzd3oz@treble>
 <xhsmh8raws53o.mognet@vschneid.remote.csb>
 <20230731213631.pywytiwdqgtgx4ps@treble>
 <20230731214612.GC51835@hirez.programming.kicks-ass.net>
 <20230801160636.ko3oc4cwycwejyxy@treble>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230801160636.ko3oc4cwycwejyxy@treble>
Precedence: bulk

On Tue, Aug 01, 2023 at 11:06:36AM -0500, Josh Poimboeuf wrote:
> On Mon, Jul 31, 2023 at 11:46:12PM +0200, Peter Zijlstra wrote:
> > > Ideally it would only print a single warning for this case, something
> > > like:
> > > 
> > >   vmlinux.o: warning: objtool: __flush_tlb_all_noinstr+0x4: indirect call to native_flush_tlb_local() leaves .noinstr.text section
> > 
> > But then what for the case where there are multiple implementations and
> > more than one isn't noinstr?
> 
> The warning would be in the loop in pv_call_dest(), so it would
> potentially print multiple warnings, one for each potential dest.
> 
> > IIRC that is where these double prints came from. One is the callsite
> > (always one) and the second is the offending implementation (but there
> > could be more).
> 
> It's confusing to warn about the call site and the destination in two
> separate warnings.  That's why I'm proposing combining them into a
> single warning (which still could end up as multiple warnings if there
> are multiple affected dests).
> 
> > > I left out "pv_ops[1]" because it's already long enough :-)
> > 
> > The index number is useful when also looking at the assembler, which
> > IIRC is an indexed indirect call.
> 
> Ok, so something like so?
> 
>   vmlinux.o: warning: objtool: __flush_tlb_all_noinstr+0x4: indirect call to pv_ops[1] (native_flush_tlb_local) leaves .noinstr.text section

Sure, that all would work I suppose.