Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 17 Apr 2020 23:56:01 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc:     Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        "David (ChunMing) Zhou" <David1.Zhou@amd.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jann Horn <jannh@google.com>, Leo Li <sunpeng.li@amd.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        amd-gfx@lists.freedesktop.org, Ingo Molnar <mingo@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Harry Wentland <harry.wentland@amd.com>, mhiramat@kernel.org
Subject: Re: AMD DC graphics display code enables -mhard-float, -msse, -msse2
 without any visible FPU state protection
Message-ID: <20200417215601.GQ2483@worktop.programming.kicks-ass.net>
References: <CAG48ez2Sx4ELkM94aD_h_J7K7KBOeuGmvZLKRkg3n_f2WoZ_cg@mail.gmail.com>
 <4c5fe55d-9db9-2f61-59b2-1fb2e1b45ed0@amd.com>
 <20200402141308.GB20730@hirez.programming.kicks-ass.net>
 <20200409155956.GQ20760@hirez.programming.kicks-ass.net>
 <20200409170916.GR20760@hirez.programming.kicks-ass.net>
 <87a2f2fc-972d-ab9b-a29d-72f02d94e60e@amd.com>
 <20200409200125.GB2483@worktop.programming.kicks-ass.net>
 <20200417202728.w2v3frkxqsgutb7h@outlook.office365.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200417202728.w2v3frkxqsgutb7h@outlook.office365.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Apr 17, 2020 at 04:27:28PM -0400, Rodrigo Siqueira wrote:
> I'm going to work on the FPU issues in the display code. In this sense,
> could you clarify a little bit more about the Makefile issues?

I think it might have been PEBKAC, I assumed allmodconfig would end up
selecting the driver, it doesn't!

Adding "AMD GPU" to a defconfig seems to make it work:

$ make O=defconfig-build/ drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o

Sorry about the confusion.

> Also, I applied the patch `[PATCH v4] x86: insn: Add insn_is_fpu()` and
> tried to reproduce the warning that you described but I didn't see it.
> Could you explain to me how I can check those warnings?

grab:

  git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/fpu

Then build like above:

$ make O=defconfig-build/ drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o

And manually validate:

$ defconfig-build/tools/objtool/objtool check -Ffa defconfig-build/drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o
defconfig-build/drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o: warning: objtool: dcn_validate_bandwidth()+0x1b17: FPU instruction outside of kernel_fpu_{begin,end}()