Date: Thu, 4 Jan 2018 08:37:02 -0800
From: Andi Kleen <ak@linux.intel.com>
To: Juergen Gross <jgross@suse.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>, Paul Turner <pjt@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linux-foundation.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Dave Hansen <dave.hansen@intel.com>, tglx@linutronix.de,
        Kees Cook <keescook@google.com>,
        Rik van Riel <riel@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Jiri Kosina <jikos@kernel.org>, gnomes@lxorguk.ukuu.org.uk
Subject: Re: [PATCH v3 10/13] x86/retpoline/pvops: Convert assembler indirect
 jumps
Message-ID: <20180104163702.GM25156@tassilo.jf.intel.com>
References: <20180104143710.8961-1-dwmw@amazon.co.uk>
 <20180104143710.8961-10-dwmw@amazon.co.uk>
 <380dc816-1732-90dc-268e-4a8c3e7ccc7d@suse.com>
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On Thu, Jan 04, 2018 at 04:02:06PM +0100, Juergen Gross wrote:
> On 04/01/18 15:37, David Woodhouse wrote:
> > Convert pvops invocations to use non-speculative call sequences, when
> > CONFIG_RETPOLINE is enabled.
> > 
> > There is scope for future optimisation here — once the pvops methods are
> > actually set, we could just turn the damn things into *direct* jumps.
> > But this is perfectly sufficient for now, without that added complexity.
> 
> I don't see the need to modify the pvops calls.
> 
> All indirect calls are replaced by either direct calls or other code
> long before any user code is active.
> 
> For modules the replacements are in place before the module is being
> used.

Agreed. This shouldn't be needed.

-Andi