From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 21 May 2008 21:09:58 +0900 Subject: Re: [PATCH 1/4] block: use ARCH_KMALLOC_MINALIGN as the default dma pad mask From: FUJITA Tomonori In-Reply-To: <20080521112554.GA19558@gondor.apana.org.au> References: <20080521100529.GA19077@gondor.apana.org.au> <20080521200104C.tomof@acm.org> <20080521112554.GA19558@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20080521210956C.tomof@acm.org> Sender: owner-linux-mm@kvack.org Return-Path: To: herbert@gondor.apana.org.au Cc: fujita.tomonori@lab.ntt.co.jp, akpm@linux-foundation.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, jens.axboe@oracle.com, tsbogend@alpha.franken.de, bzolnier@gmail.com, James.Bottomley@HansenPartnership.com, jeff@garzik.org, davem@davemloft.net, linux-mm@kvack.org List-ID: On Wed, 21 May 2008 19:25:54 +0800 Herbert Xu wrote: > On Wed, May 21, 2008 at 08:01:12PM +0900, FUJITA Tomonori wrote: > > > > Why do algorithms require alignments bigger than ARCH_KMALLOC_MINALIGN? > > Because the hardware may require it. For example, the VIA Padlock > will fault unless the buffers are 16-byte aligned (it being an > x86-32 platform). OK, thanks. So it's about hardware requrement. Let me make sure if I understand crypto alignment issue. __crt_ctx needs ARCH_KMALLOC_MINALIGN alignment only because of crypto hardware. If I misunderstand it, can you answer my question in the previous mail (it's the part that you cut)? That is, why does __crt_ctx need ARCH_KMALLOC_MINALIGN alignment with software algorithms. The VIA Padlock likes 16-byte aligned __crt_ctx. On x86-32 platform, ARCH_KMALLOC_MINALIGN is not defined, so __crt_ctx is 8-byte aligned. struct aes_ctx of The VIA Padlock may not be aligned so you may need ALIGN hack every time. But ARCH_KMALLOC_MINALIGN is 128 bytes on some architectures. In this case, __crt_ctx is 128-byte aligned and struct aes_ctx of The VIA Padlock is guaranteed to be aligned nicely. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org