Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754263AbYFYUJ3 (ORCPT ); Wed, 25 Jun 2008 16:09:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751144AbYFYUJW (ORCPT ); Wed, 25 Jun 2008 16:09:22 -0400 Received: from casper.infradead.org ([85.118.1.10]:46094 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbYFYUJV (ORCPT ); Wed, 25 Jun 2008 16:09:21 -0400 Date: Wed, 25 Jun 2008 13:09:18 -0700 From: Arjan van de Ven To: Agner Fog Cc: linux-kernel@vger.kernel.org Subject: Re: ABI change for device drivers using future AVX instruction set Message-ID: <20080625130918.53ae744b@infradead.org> In-Reply-To: <4862A25C.2060703@agner.org> References: <48626514.2040905@agner.org> <20080625092224.736c2541@infradead.org> <4862A25C.2060703@agner.org> Organization: Intel X-Mailer: Claws Mail 3.3.1 (GTK+ 2.12.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1484 Lines: 39 On Wed, 25 Jun 2008 21:54:04 +0200 Agner Fog wrote: > Arjan van de Ven wrote: > >Let me repeat this loud and clear: > >It is not allowed to use floating point, SSE of AVX in device > >drivers. > > Thank you for a clear answer. Re-reading the ABI: > >A.2.4 Miscellaneous Remarks > >Linux Kernel code is not allowed to change the x87 and SSE units. > >If > those are > >changed by kernel code, they have to be restored properly before > sleeping or leaving > >the kernel. On preemptive kernels also more precautions may be > >needed. > > This states your point, but certainly not "loud and clear" :-) > > This ABI statement has to be amended, however, because it is allowed the linux kernel policy is loud and clear; this is more an OS policy as it is a platform ABI issue. We as linux do not allow this (with the small footnote around the raid stuff, but that has specific very careful use). In addition, you really aren't allowed to use floating point in the kernel period as concept, if you need it you very likely are doing something wrong. -- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/