Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932374AbVJQX0q (ORCPT ); Mon, 17 Oct 2005 19:26:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932375AbVJQX0p (ORCPT ); Mon, 17 Oct 2005 19:26:45 -0400 Received: from mail.dvmed.net ([216.237.124.58]:9361 "EHLO mail.dvmed.net") by vger.kernel.org with ESMTP id S932374AbVJQX0p (ORCPT ); Mon, 17 Oct 2005 19:26:45 -0400 Message-ID: <43543331.6030603@pobox.com> Date: Mon, 17 Oct 2005 19:26:41 -0400 From: Jeff Garzik User-Agent: Mozilla Thunderbird 1.0.7-1.1.fc4 (X11/20050929) X-Accept-Language: en-us, en MIME-Version: 1.0 To: "H. Peter Anvin" CC: linux-kernel@vger.kernel.org Subject: Re: [RFC] RNG rewrite... References: <20051015043120.GA5946@plexity.net> <4350DCB1.7010201@pobox.com> <20051016005341.GB5946@plexity.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: 0.0 (/) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1477 Lines: 34 H. Peter Anvin wrote: > Followup to: <20051016005341.GB5946@plexity.net> > By author: Deepak Saxena > In newsgroup: linux.dev.kernel > >>It's a magic regsiter we just read/write and could be done in userspace. >>I also took a look at MPC85xx and it has the same sort of interface but >>also has an error interrupt capability. On second thought a class >>interface is overkill b/c there will only be one RNG per system, so >>I can just do something like watchdogs where we have a bunch of simple >>drivers exposing the same interface. We could do it in user space but >>then we have separate RNG implementations for x86 and !x86 and I'd >>rather not see that. Can we move the x86 code out to userspace and >>just let the daemon eat the numbers directly from HW? We can mmap() >>PCI devices, but I don't know enough about x86 to say whether msr >>instructions can execute out of userspace (or if we want them to...). > MSR instructions cannot execute out of userspace, but the MSR driver > might be possible to use. It's usually quite slow, however. MSRs are used for setup, not for actual data. Intel: magic MMIO address (readb) AMD: magic PIO address (inl) VIA: CPU instruction ('xstore') Jeff - 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/