From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Fri, 27 Jul 2018 14:22:44 +0100
Subject: [RFC PATCH] arm64: mm: Export __sync_icache_dcache() for
 xen-privcmd
In-Reply-To: <20180727120633.bjpfqswuxcy2ibqu@armageddon.cambridge.arm.com>
References: <20180711231822.GG14131@decadent.org.uk>
 <20180727120633.bjpfqswuxcy2ibqu@armageddon.cambridge.arm.com>
Message-ID: <20180727132243.GA28549@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Fri, Jul 27, 2018 at 01:06:33PM +0100, Catalin Marinas wrote:
> On Thu, Jul 12, 2018 at 12:18:22AM +0100, Ben Hutchings wrote:
> > The xen-privcmd driver, which can be modular, calls set_pte_at()
> > which in turn may call __sync_icache_dcache().
> > 
> > The call to __sync_icache_dcache() may be optimised out because it is
> > conditional on !pte_special(), and xen-privcmd calls pte_mkspecial().
> > But it seems unwise to rely on this optimisation.
> > 
> > Fixes: 3ad0876554ca ("xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE")
> > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > ---
> > This is an RFC since I haven't found an actual build failure.  Using
> > Debian's gcc 7.3 with either CC_OPTIMIZE_FOR_PERFORMANCE or
> > CC_OPTIMIZE_FOR_SIZE, the call *is* optimised away.
> 
> Since apply_to_page_range() is EXPORT_SYMBOL_GPL() and a
> pte_fn_t function would likely use set_pte_at(), I'm fine with this
> patch for consistency.
> 
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>

Okey doke, I'll pick this up for 4.19.

Will