Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750824AbWBWE0h (ORCPT ); Wed, 22 Feb 2006 23:26:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750826AbWBWE0h (ORCPT ); Wed, 22 Feb 2006 23:26:37 -0500 Received: from e36.co.us.ibm.com ([32.97.110.154]:64422 "EHLO e36.co.us.ibm.com") by vger.kernel.org with ESMTP id S1750824AbWBWE0g (ORCPT ); Wed, 22 Feb 2006 23:26:36 -0500 Message-ID: <43FD3971.7070703@us.ibm.com> Date: Wed, 22 Feb 2006 22:26:25 -0600 From: Anthony Liguori User-Agent: Mail/News 1.5 (X11/20060213) MIME-Version: 1.0 To: Arjan van de Ven CC: "Mike D. Day" , Heiko Carstens , Dave Hansen , xen-devel@lists.xensource.com, lkml , Greg KH Subject: Re: [ PATCH 2.6.16-rc3-xen 3/3] sysfs: export Xen hypervisor attributes to sysfs References: <43FB2642.7020109@us.ibm.com> <1140542130.8693.18.camel@localhost.localdomain> <20060222123250.GB9295@osiris.boeblingen.de.ibm.com> <43FC5B1D.5040901@us.ibm.com> <1140612969.2979.20.camel@laptopd505.fenrus.org> <43FC61C4.30002@us.ibm.com> <20060222131918.GC9295@osiris.boeblingen.de.ibm.com> <43FC6A86.90901@us.ibm.com> <1140616911.2979.22.camel@laptopd505.fenrus.org> In-Reply-To: <1140616911.2979.22.camel@laptopd505.fenrus.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2008 Lines: 50 Arjan van de Ven wrote: > On Wed, 2006-02-22 at 08:43 -0500, Mike D. Day wrote: > >> Heiko Carstens wrote: >> >>> On Wed, Feb 22, 2006 at 08:06:12AM -0500, Mike D. Day wrote: >>> >>> If it's not needed, why include it at all? >>> >> Sorry for not being clear. It *is* needed for control tools and agents >> running in the privileged domain. >> > > but again those tools and agents *already* have a way of talking to the > hypervisor themselves. Why can't they just first ask this info? Why does > that need to be in the kernel, in unswappable memory? > Hypercalls have to be done in ring 0 for security reasons) There has to be some kernel interface for making hypercalls. The current interface is a ioctl() on a /proc file (which is awful). The ioctl just pretty much passes 5 word arguments to the hypervisor. It was suggested previously here that a hypercall pass-through interface isn't the right approach. One suggestion that came up was a syscall interface. Also, there are some kernel-level drivers, like the memory ballooning driver, that only exist in the kernel. Controlling the balloon driver requires some sort of interface. That was the original point of this effort (since it's currently exposed as a /proc file). I think it's quite clear that the balloon driver should expose itself through sysfs but I'm not personally convinced that this information (hypervisor version information) ought to be exposed in sysfs. Regards, Anthony Liguori > - > 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/ > > - 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/