linux-kernel - Re: [PATCH v2 06/18] arm64: kvm: use -fno-jump-tables with clang

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Date:   Thu, 16 Nov 2017 11:46:17 +0000
From:   Will Deacon <will.deacon@....com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Alex Matveev <alxmtvv@...il.com>, Andi Kleen <ak@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Maxim Kuvyrkov <maxim.kuvyrkov@...aro.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH v2 06/18] arm64: kvm: use -fno-jump-tables with clang

On Wed, Nov 15, 2017 at 01:34:16PM -0800, Sami Tolvanen wrote:
> Use -fno-jump-tables to make sure clang doesn't generate branches
> to EL1 virtual addresses.

Can you elaborate a bit more on exactly what you saw failing here, please?
Whilst it's obviously broken to jump to EL1 from EL2 w/o VHE, the commit
message is a bit cryptic.

Will