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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Sat, 21 Nov 2020 00:30:32 +0100
Message-ID: <CAMj1kXEoPEd6GzjL1XuxTPwitbR03BiBEXpAGtUytMj-h=vCkg@mail.gmail.com>
Subject: Re: [PATCH v7 00/17] Add support for Clang LTO
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Sami Tolvanen <samitolvanen@google.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Will Deacon <will@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        PCI <linux-pci@vger.kernel.org>,
        Alistair Delva <adelva@google.com>
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On Fri, 20 Nov 2020 at 21:19, Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> On Fri, Nov 20, 2020 at 2:30 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > On Thu, 19 Nov 2020 at 00:42, Nick Desaulniers <ndesaulniers@google.com> wrote:
> > >
> > > Thanks for continuing to drive this series Sami.  For the series,
> > >
> > > Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> > >
> > > I did virtualized boot tests with the series applied to aarch64
> > > defconfig without CONFIG_LTO, with CONFIG_LTO_CLANG, and a third time
> > > with CONFIG_THINLTO.  If you make changes to the series in follow ups,
> > > please drop my tested by tag from the modified patches and I'll help
> > > re-test.  Some minor feedback on the Kconfig change, but I'll post it
> > > off of that patch.
> > >
> >
> > When you say 'virtualized" do you mean QEMU on x86? Or actual
> > virtualization on an AArch64 KVM host?
>
> aarch64 guest on x86_64 host.  If you have additional configurations
> that are important to you, additional testing help would be
> appreciated.
>

Could you run this on an actual phone? Or does Android already ship
with this stuff?


> >
> > The distinction is important here, given the potential impact of LTO
> > on things that QEMU simply does not model when it runs in TCG mode on
> > a foreign host architecture.
>
> --
> Thanks,
> ~Nick Desaulniers