From: Michael Ellerman <michael@ellerman.id.au>
Subject: Re: [PATCH 3/4] powerpc/crypto: add 842 hardware compression driver
Date: Fri, 20 Jul 2012 15:33:30 +1000
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Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Kent Yoder <key@linux.vnet.ibm.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
	Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Robert Jennings <rcj@linux.vnet.ibm.com>,
	linuxppc-dev@lists.ozlabs.org,
	"David S. Miller" <davem@davemloft.net>,
	linux-crypto@vger.kernel.org
To: Seth Jennings <sjenning@linux.vnet.ibm.com>
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On Thu, 2012-07-19 at 09:42 -0500, Seth Jennings wrote:
> This patch adds the driver for interacting with the 842
> compression accelerator on IBM Power7+ systems.

...

> +struct nx842_slentry {
> +	unsigned long ptr; /* Absolute address (use virt_to_abs()) */
> /+	unsigned long len;
> +};

These days virt_to_abs() is just __pa() - ie. convert to a real address.

So you should just use __pa().

And you also need to be certain that you only call it on addresses where
that makes sense, ie. not vmalloc etc.

cheers