From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756818AbZEERDV (ORCPT ); Tue, 5 May 2009 13:03:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754816AbZEERDK (ORCPT ); Tue, 5 May 2009 13:03:10 -0400 Received: from e8.ny.us.ibm.com ([32.97.182.138]:37900 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754737AbZEERDJ (ORCPT ); Tue, 5 May 2009 13:03:09 -0400 Subject: Re: [RFC PATCH 1/3] add generic hypercall support From: Hollis Blanchard To: Gregory Haskins Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, avi@redhat.com In-Reply-To: <20090505132437.19891.42922.stgit@dev.haskins.net> References: <20090505132005.19891.78436.stgit@dev.haskins.net> <20090505132437.19891.42922.stgit@dev.haskins.net> Content-Type: text/plain Organization: IBM Linux Technology Center Date: Tue, 05 May 2009 12:03:07 -0500 Message-Id: <1241542987.24786.76.camel@slate.austin.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.24.5 (2.24.5-1.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2009-05-05 at 09:24 -0400, Gregory Haskins wrote: > > *) PIO is more direct than MMIO, but it poses other problems such as: > a) can have a small limited address space (x86 is 2^16) > b) is a narrow-band interface (one 8, 16, 32, 64 bit word at a time) > c) not available on all archs (PCI mentions ppc as problematic) and > is therefore recommended to avoid. Side note: I don't know what PCI has to do with this, and "problematic" isn't the word I would use. ;) As far as I know, x86 is the only still-alive architecture that implements instructions for a separate IO space (not even ia64 does). -- Hollis Blanchard IBM Linux Technology Center