linux-kernel - Re: [PATCH v7 09/11] arm64: disable SCS for hypervisor code

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Message-ID: <CABCJKucpq=zu7ikf+Q-f-v+6T-cbQCEb1setiZfFvHa8iw3erg@mail.gmail.com>
Date:   Wed, 12 Feb 2020 09:30:49 -0800
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Dave Martin <Dave.Martin@....com>,
        Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 09/11] arm64: disable SCS for hypervisor code

On Tue, Feb 11, 2020 at 1:54 AM Will Deacon <will@...nel.org> wrote:
> Thanks, I missed that. It's annoying that we'll end up needing /both/
> -ffixed-x18 *and* the save/restore around guest transitions, but if we
> actually want to use SCS for the VHE code then I see that it will be
> required.
>
> Sami -- can you restore -ffixed-x18 and then try the function attribute
> as suggested by James, please?

Sure. Adding __noscs to __hyp_text and not filtering out any of the
flags in the Makefile appears to work. I'll update this in the next
version.

Sami