From: "Nicholas A. Bellinger" Subject: Re: [RFC 12/12] iscsi-target: Add Makefile/Kconfig and update TCM top level Date: Thu, 03 Mar 2011 12:58:25 -0800 Message-ID: <1299185905.5401.405.camel@haakon2.linux-iscsi.org> References: <1299036841-23677-1-git-send-email-nab@linux-iscsi.org> <1299036841-23677-13-git-send-email-nab@linux-iscsi.org> <20110301223251.11c95eed.rdunlap@xenotime.net> <1299101531.5401.313.camel@haakon2.linux-iscsi.org> <20110303141928.GA25256@infradead.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Randy Dunlap , linux-scsi , linux-kernel , linux-crypto@vger.kernel.org, James Bottomley To: Christoph Hellwig Return-path: In-Reply-To: <20110303141928.GA25256@infradead.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On Thu, 2011-03-03 at 09:19 -0500, Christoph Hellwig wrote: > On Wed, Mar 02, 2011 at 01:32:11PM -0800, Nicholas A. Bellinger wrote: > > The kernel code itself that is specific to using the SSE v4.2 > > instruction for CRC32C offload are using #ifdef CONFIG_X86 stubs in > > iscsi_target_login.c:iscsi_login_setup_crypto(), and !CONFIG_X86 will > > default to using the unoptimized 1x8 slicing soft CRC32C code. This > > particular piece of logic has been tested on powerpc and arm and is > > funcitoning as expected from the kernel level using the arch independent > > soft code. > > I don't think you need that code at all. The crypto code is structured > to prefer the optimized implementation if it is present. Just stripping > the x86-specific code out and always requesting the plain crc32c > algorithm should give you the optimized one if it is present on your > system. > > Please give it a try. > This is what I originally thought as well, but this ended up not being the case when the logic was originally coded up. I just tried again with .38-rc7 on a 5500 series machine and simply stubbing out the CONFIG_X86 part from iscsi_login_setup_crypto() and calling: crypto_alloc_hash("crc32c", 0, CRYPTO_ALG_ASYNC) does not automatically load and use crc32c_intel.ko when only requesting plain crc32c. The reason for the extra crypto_alloc_hash("crc32c-intel", ...) call in iscsi_login_setup_crypto() is to load crc32c_intel.ko on-demand for cpu_has_xmm4_2 capable machines. I should mention this is with the following .config: CONFIG_CRYPTO_CRC32C=y CONFIG_CRYPTO_CRC32C_INTEL=m This would seem to indicate that CRC32C_INTEL needs to be compiled in (or at least manually loaded) for libcypto to use the optimized instructions when the plain crc32c is called, correct..? --nab