From: Herbert Xu Subject: Re: [PATCH v6 2/8] crypto: add driver-side scomp interface Date: Thu, 23 Jun 2016 18:50:34 +0800 Message-ID: <20160623105034.GA10475@gondor.apana.org.au> References: <1465373818-29720-1-git-send-email-giovanni.cabiddu@intel.com> <1465373818-29720-3-git-send-email-giovanni.cabiddu@intel.com> <20160613085612.GA7333@gondor.apana.org.au> <20160622155350.GA22247@sivswdev01.ir.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-crypto@vger.kernel.org To: Giovanni Cabiddu Return-path: Received: from helcar.hengli.com.au ([209.40.204.226]:47772 "EHLO helcar.hengli.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751616AbcFWKuk (ORCPT ); Thu, 23 Jun 2016 06:50:40 -0400 Content-Disposition: inline In-Reply-To: <20160622155350.GA22247@sivswdev01.ir.intel.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Wed, Jun 22, 2016 at 04:53:50PM +0100, Giovanni Cabiddu wrote: > On Mon, Jun 13, 2016 at 04:56:12PM +0800, Herbert Xu wrote: > > The backup path is also very unlikely to work because we'll be > > hitting this with 64K sizes and this just won't work with a 4K > > page size. > Is scatterwalk_map_and_copy broken? No that's not the problem. The problem is that you can't kmalloc 64K of memory. kmalloc requires physically contiguous memory and you cannot rely on having 64K of contiguous memory. > > This totally breaks down once you go to DMA, where an SG list is > > required. > scomp backends should be used only for software implementations. > A driver backend which needs DMA should plug into acomp. What I'm saying is that the current strategy of using vmalloc memory as input/output buffers cannot possibly work with acomp since you cannot do DMA over vmalloc memory. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt