linux-kernel - Re: [PATCH v4 03/17] arm64: kvm: stop treating register x18 as caller save

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Date:   Mon, 04 Nov 2019 12:13:00 +0109
From:   Marc Zyngier <maz@...nel.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Will Deacon <will@...nel.org>,
        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>,
        Mark Rutland <mark.rutland@....com>,
        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@...glegroups.com>,
        <kernel-hardening@...ts.openwall.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 03/17] arm64: kvm: stop treating register x18 as  caller save

Hi Sami,

On 2019-11-01 23:20, Sami Tolvanen wrote:
> From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>
> In preparation of reserving x18, stop treating it as caller save in
> the KVM guest entry/exit code. Currently, the code assumes there is
> no need to preserve it for the host, given that it would have been
> assumed clobbered anyway by the function call to __guest_enter().
> Instead, preserve its value and restore it upon return.
>
> Link: https://patchwork.kernel.org/patch/9836891/
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> [Sami: updated commit message, switched from x18 to x29 for the guest
> context]
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>

If you intend for this to be merged via the arm64 tree, please add my

Reviewed-by: Marc Zyngier <marc.zyngier@....com>

Thanks,

         M.
-- 
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