From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [PATCH 2/3] x86_64: Define 128-bit memory-mapped I/O operations Date: Wed, 22 Aug 2012 03:04:11 +0100 Message-ID: <1345601051.2659.93.camel@bwh-desktop.uk.solarflarecom.com> References: <1345598275.2659.71.camel@bwh-desktop.uk.solarflarecom.com> <1345598601.2659.76.camel@bwh-desktop.uk.solarflarecom.com> <503437D4.8090706@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Thomas Gleixner , Ingo Molnar , , , To: "H. Peter Anvin" Return-path: Received: from webmail.solarflare.com ([12.187.104.25]:55617 "EHLO ocex02.SolarFlarecom.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754863Ab2HVCEP (ORCPT ); Tue, 21 Aug 2012 22:04:15 -0400 In-Reply-To: <503437D4.8090706@zytor.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2012-08-21 at 18:37 -0700, H. Peter Anvin wrote: > On 08/21/2012 06:23 PM, Ben Hutchings wrote: > > Define reado(), writeo() and their raw counterparts using SSE. > > > > Based on work by Stuart Hodgson . > > It would be vastly better if we explicitly controlled this with > kernel_fpu_begin()/kernel_fpu_end() rather than hiding it in primitives > than might tempt the user to do very much the wrong thing. > > Also, it needs to be extremely clear to the user that these operations > use the FPU, and all the requirements there need to be met, including > not using them at interrupt time. Well we can sometimes use the FPU state at IRQ time, can't we (irq_fpu_usable())? So we might need, say, try_reado() and try_writeo() with callers expected to fall back to alternatives. (Which they must have anyway for any architecture that doesn't support this.) Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.