Hi, I am a newbie for the XEN area and curious to know whether current XEN could support nommu arch, or only MPU? If current it doesn''t support, does XEN have any plan or road map to add this support in future? Thanks, Lei
On Tue, 2012-08-14 at 10:31 +0100, Lei Wen wrote:> Hi, > > I am a newbie for the XEN area and curious to know whether current XEN > could support nommu arch, or only MPU? > If current it doesn''t support, does XEN have any plan or road map to > add this support in future?You should be able to run a NOMMU guest OS as an HVM guest today (or at least I can''t think why it wouldn''t work). There are no plans to make Xen itself usable on a no-MMU system, use of the MMU is pretty firmly baked into Xens architecture. Ian.
Hi Ian, On Tue, Aug 14, 2012 at 9:06 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote:> On Tue, 2012-08-14 at 10:31 +0100, Lei Wen wrote: >> Hi, >> >> I am a newbie for the XEN area and curious to know whether current XEN >> could support nommu arch, or only MPU? >> If current it doesn''t support, does XEN have any plan or road map to >> add this support in future? > > You should be able to run a NOMMU guest OS as an HVM guest today (or at > least I can''t think why it wouldn''t work). > > There are no plans to make Xen itself usable on a no-MMU system, use of > the MMU is pretty firmly baked into Xens architecture.Yep, I get your point. However, on modern embedded system, there are still place for no-mmu arches, like the ARM cortex-r7 processor: http://www.arm.com/products/processors/cortex-r/cortex-r7.php So making such platform virtualised would have the business benefit, since could reduce total embedded product BOM price. Do you have any guideline or idea that could make nommu possible? :) I would like to take the chance to investigate whether we could enable it on XEN. Thanks, Lei
On Tue, 2012-08-14 at 14:23 +0100, Lei Wen wrote:> Hi Ian, > > On Tue, Aug 14, 2012 at 9:06 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > > On Tue, 2012-08-14 at 10:31 +0100, Lei Wen wrote: > >> Hi, > >> > >> I am a newbie for the XEN area and curious to know whether current XEN > >> could support nommu arch, or only MPU? > >> If current it doesn''t support, does XEN have any plan or road map to > >> add this support in future? > > > > You should be able to run a NOMMU guest OS as an HVM guest today (or at > > least I can''t think why it wouldn''t work). > > > > There are no plans to make Xen itself usable on a no-MMU system, use of > > the MMU is pretty firmly baked into Xens architecture. > > Yep, I get your point. However, on modern embedded system, there are still > place for no-mmu arches, like the ARM cortex-r7 processor: > http://www.arm.com/products/processors/cortex-r/cortex-r7.phpOK, you should have made it clear you were talking about ARM. The ARM port which I am involved with[0] requires the virtualisation extensions, which AFAIK are a ARMv7-A only and an MMU is always assumed (it''s presence pretty much baked into the extensions in various ways). We have no plans to support non-mmu ports of this variant of Xen. The other ARM port (the PV port[1]) does not require virtualisation extensions, however the correct list for questions/discussion about that port is the xen-arm@ list. [0] http://wiki.xen.org/wiki/Xen_ARMv7_with_Virtualization_Extensions [1] http://wiki.xen.org/wiki/Xen_ARM_%28PV%29> So making such platform virtualised would have the business benefit, since > could reduce total embedded product BOM price. > > Do you have any guideline or idea that could make nommu possible? :)Even the ARM PV port makes extensive use of the MMU to provide isolation between guests (at least I presume so). If you want to work on nommu systems then it seems like this would be the first problem you would have to consider. Ian.
On Tue, Aug 14, 2012 at 9:35 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote:> On Tue, 2012-08-14 at 14:23 +0100, Lei Wen wrote: >> Hi Ian, >> >> On Tue, Aug 14, 2012 at 9:06 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote: >> > On Tue, 2012-08-14 at 10:31 +0100, Lei Wen wrote: >> >> Hi, >> >> >> >> I am a newbie for the XEN area and curious to know whether current XEN >> >> could support nommu arch, or only MPU? >> >> If current it doesn''t support, does XEN have any plan or road map to >> >> add this support in future? >> > >> > You should be able to run a NOMMU guest OS as an HVM guest today (or at >> > least I can''t think why it wouldn''t work). >> > >> > There are no plans to make Xen itself usable on a no-MMU system, use of >> > the MMU is pretty firmly baked into Xens architecture. >> >> Yep, I get your point. However, on modern embedded system, there are still >> place for no-mmu arches, like the ARM cortex-r7 processor: >> http://www.arm.com/products/processors/cortex-r/cortex-r7.php > > OK, you should have made it clear you were talking about ARM. > > The ARM port which I am involved with[0] requires the virtualisation > extensions, which AFAIK are a ARMv7-A only and an MMU is always assumed > (it''s presence pretty much baked into the extensions in various ways). > We have no plans to support non-mmu ports of this variant of Xen. > > The other ARM port (the PV port[1]) does not require virtualisation > extensions, however the correct list for questions/discussion about that > port is the xen-arm@ list. > > [0] http://wiki.xen.org/wiki/Xen_ARMv7_with_Virtualization_Extensions > [1] http://wiki.xen.org/wiki/Xen_ARM_%28PV%29 > >> So making such platform virtualised would have the business benefit, since >> could reduce total embedded product BOM price. >> >> Do you have any guideline or idea that could make nommu possible? :) > > Even the ARM PV port makes extensive use of the MMU to provide isolation > between guests (at least I presume so). If you want to work on nommu > systems then it seems like this would be the first problem you would > have to consider. >Understand. Thanks for your kindly reply. :) Thanks, Lei