linux-kernel - Re: [PATCH v4 13/17] arm64: preserve x18 when CPU is suspended

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Message-ID: <CABCJKucVON6uUMH6hVP7RODqH8u63AP3SgTCBWirrS30yDOmdA@mail.gmail.com>
Date:   Mon, 4 Nov 2019 13:38:30 -0800
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
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 <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 v4 13/17] arm64: preserve x18 when CPU is suspended

On Mon, Nov 4, 2019 at 5:20 AM Marc Zyngier <maz@...nel.org> wrote:
> >  ENTRY(cpu_do_suspend)
> >       mrs     x2, tpidr_el0
> > @@ -73,6 +75,9 @@ alternative_endif
> >       stp     x8, x9, [x0, #48]
> >       stp     x10, x11, [x0, #64]
> >       stp     x12, x13, [x0, #80]
> > +#ifdef CONFIG_SHADOW_CALL_STACK
> > +     str     x18, [x0, #96]
> > +#endif
>
> Do we need the #ifdefery here? We didn't add that to the KVM path,
> and I'd feel better having a single behaviour, specially when
> NR_CTX_REGS is unconditionally sized to hold 13 regs.

I'm fine with dropping the ifdefs here in v5 unless someone objects to this.

Sami