Re: [Xen-devel] Future of 32-bit PV support
On 20/08/18 17:31, Manuel Bouyer wrote: > On Thu, Aug 16, 2018 at 08:17:13AM +0200, Juergen Gross wrote: >> In the Xen x86 community call we have been discussing whether anyone >> really is depending on 32-bit PV guests. We'd like to evaluate whether >> anyone would see problems with: >> >> - deprecating 32-bit PV guest support in Xen, meaning that we'd >> eventually switch to support 32-bit PV guests only via PV-shim from >> Xen 4.12 or 4.13 >> >> - dropping 32-bit PV support from upstream Linux kernel, resulting in >> current 32-bit PV guests no longer being able to upgrade to the newest >> kernel version any longer >> >> And related to that: >> >> - is there any Linux distribution still shipping 32-bit PV-capable >> systems? >> >> - what about BSD? Is 32-bit PV support important there? > > Hello, > Actually, NetBSD only supports PV (there is work toward PV drivers for HVM, > and PVH, but this is making slow progress). 32-bit PV is faster than 64-bit PV > so all my domUs are 32bits these days. Thanks for the feedback. Juergen ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
On Thu, Aug 16, 2018 at 08:17:13AM +0200, Juergen Gross wrote: > In the Xen x86 community call we have been discussing whether anyone > really is depending on 32-bit PV guests. We'd like to evaluate whether > anyone would see problems with: > > - deprecating 32-bit PV guest support in Xen, meaning that we'd > eventually switch to support 32-bit PV guests only via PV-shim from > Xen 4.12 or 4.13 > > - dropping 32-bit PV support from upstream Linux kernel, resulting in > current 32-bit PV guests no longer being able to upgrade to the newest > kernel version any longer > > And related to that: > > - is there any Linux distribution still shipping 32-bit PV-capable > systems? > > - what about BSD? Is 32-bit PV support important there? Hello, Actually, NetBSD only supports PV (there is work toward PV drivers for HVM, and PVH, but this is making slow progress). 32-bit PV is faster than 64-bit PV so all my domUs are 32bits these days. -- Manuel Bouyer NetBSD: 26 ans d'experience feront toujours la difference -- ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
On 16/08/18 19:34, Stefano Stabellini wrote: > On Thu, 16 Aug 2018, Juergen Gross wrote: >> In the Xen x86 community call we have been discussing whether anyone >> really is depending on 32-bit PV guests. We'd like to evaluate whether >> anyone would see problems with: >> >> - deprecating 32-bit PV guest support in Xen, meaning that we'd >> eventually switch to support 32-bit PV guests only via PV-shim from >> Xen 4.12 or 4.13 >> >> - dropping 32-bit PV support from upstream Linux kernel, resulting in >> current 32-bit PV guests no longer being able to upgrade to the newest >> kernel version any longer >> >> And related to that: >> >> - is there any Linux distribution still shipping 32-bit PV-capable >> systems? >> >> - what about BSD? Is 32-bit PV support important there? > > Hi Juergen, > > Although I can see that deprecating 32-bit PV guest support is > desirable, and it might not cause any problems to Linux and > BSDs, we need to be careful about unikernels. > > There are probably unikernels out there that only support PV 32bit > still. And why not? If you are designing a unikernel today, it would > still make sense to use PV 32bit or PVH. PVH will still work, of course. 32- and 64-bit. Juergen ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
On Thu, Aug 16, 2018 at 12:55 AM, Juergen Gross wrote: > On 16/08/18 08:51, Jan Beulich wrote: > On 16.08.18 at 08:32, wrote: > >> On Wed, Aug 15, 2018 at 11:17 PM, Juergen Gross > wrote: > >> > >>> In the Xen x86 community call we have been discussing whether anyone > >>> really is depending on 32-bit PV guests. We'd like to evaluate whether > >>> anyone would see problems with: > >>> > >>> - deprecating 32-bit PV guest support in Xen, meaning that we'd > >>> eventually switch to support 32-bit PV guests only via PV-shim from > >>> Xen 4.12 or 4.13 > >>> > >>> - dropping 32-bit PV support from upstream Linux kernel, resulting in > >>> current 32-bit PV guests no longer being able to upgrade to the > newest > >>> kernel version any longer > >>> > >>> And related to that: > >>> > >>> - is there any Linux distribution still shipping 32-bit PV-capable > >>> systems? > >>> > >>> - what about BSD? Is 32-bit PV support important there? > >> > >> Juergen - just to be very clear about the scope here: > >> * would this proposal affect the ability to use a 32-bit dom0? > > > > If the Dom0 is to be PV - yes, of course. For the time being there's > > no complete PVH Dom0 support, so if 32-bit is needed here, PV is > > for now indeed the only option. > ack. I asked because it's not necessarily obvious to all that dom0 is included in the term "guest", and it widens the consequences of this change. > > And to be more precise: the first step would be to remove 32-bit PV > support from upstream Linux kernel. This would result in the loss of > the ability to use a _new_ Linux (e.g. >= 4.20 / 5.0) as a 32-bit dom0. > A 32-bit dom0 using a kernel <= 4.19 would still work until we remove > 32-bit PV support from the hypervisor (which we wouldn't do before full > support of PVH dom0, I guess). > That makes sense. > > Is there a special reason you want to use a 32-bit dom0? > In short, no. OpenXT currently uses a 32-bit PV dom0, but work is already under way to migrate to 64-bit. I think your proposal is justified and good. Christopher ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
On Thu, 16 Aug 2018, Juergen Gross wrote: > In the Xen x86 community call we have been discussing whether anyone > really is depending on 32-bit PV guests. We'd like to evaluate whether > anyone would see problems with: > > - deprecating 32-bit PV guest support in Xen, meaning that we'd > eventually switch to support 32-bit PV guests only via PV-shim from > Xen 4.12 or 4.13 > > - dropping 32-bit PV support from upstream Linux kernel, resulting in > current 32-bit PV guests no longer being able to upgrade to the newest > kernel version any longer > > And related to that: > > - is there any Linux distribution still shipping 32-bit PV-capable > systems? > > - what about BSD? Is 32-bit PV support important there? Hi Juergen, Although I can see that deprecating 32-bit PV guest support is desirable, and it might not cause any problems to Linux and BSDs, we need to be careful about unikernels. There are probably unikernels out there that only support PV 32bit still. And why not? If you are designing a unikernel today, it would still make sense to use PV 32bit or PVH. ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
On Thu, Aug 16, 2018 at 08:17:13AM +0200, Juergen Gross wrote: > In the Xen x86 community call we have been discussing whether anyone > really is depending on 32-bit PV guests. We'd like to evaluate whether > anyone would see problems with: > > - deprecating 32-bit PV guest support in Xen, meaning that we'd > eventually switch to support 32-bit PV guests only via PV-shim from > Xen 4.12 or 4.13 This means 32bit PV support would be switched off by default in the hypervisor build, but distros or individuals could still enable it (like the build system will enable it for the shim). > - dropping 32-bit PV support from upstream Linux kernel, resulting in > current 32-bit PV guests no longer being able to upgrade to the newest > kernel version any longer > > And related to that: > > - is there any Linux distribution still shipping 32-bit PV-capable > systems? > > - what about BSD? Is 32-bit PV support important there? FTR, NetBSD is the only BSD to have PV support, both 32 and 64bits. Roger. ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
On 16/08/18 08:51, Jan Beulich wrote: On 16.08.18 at 08:32, wrote: >> On Wed, Aug 15, 2018 at 11:17 PM, Juergen Gross wrote: >> >>> In the Xen x86 community call we have been discussing whether anyone >>> really is depending on 32-bit PV guests. We'd like to evaluate whether >>> anyone would see problems with: >>> >>> - deprecating 32-bit PV guest support in Xen, meaning that we'd >>> eventually switch to support 32-bit PV guests only via PV-shim from >>> Xen 4.12 or 4.13 >>> >>> - dropping 32-bit PV support from upstream Linux kernel, resulting in >>> current 32-bit PV guests no longer being able to upgrade to the newest >>> kernel version any longer >>> >>> And related to that: >>> >>> - is there any Linux distribution still shipping 32-bit PV-capable >>> systems? >>> >>> - what about BSD? Is 32-bit PV support important there? >>> >> >> >> Juergen - just to be very clear about the scope here: >> * would this proposal affect the ability to use a 32-bit dom0? > > If the Dom0 is to be PV - yes, of course. For the time being there's > no complete PVH Dom0 support, so if 32-bit is needed here, PV is > for now indeed the only option. And to be more precise: the first step would be to remove 32-bit PV support from upstream Linux kernel. This would result in the loss of the ability to use a _new_ Linux (e.g. >= 4.20 / 5.0) as a 32-bit dom0. A 32-bit dom0 using a kernel <= 4.19 would still work until we remove 32-bit PV support from the hypervisor (which we wouldn't do before full support of PVH dom0, I guess). Is there a special reason you want to use a 32-bit dom0? Juergen ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
>>> On 16.08.18 at 08:32, wrote: > On Wed, Aug 15, 2018 at 11:17 PM, Juergen Gross wrote: > >> In the Xen x86 community call we have been discussing whether anyone >> really is depending on 32-bit PV guests. We'd like to evaluate whether >> anyone would see problems with: >> >> - deprecating 32-bit PV guest support in Xen, meaning that we'd >> eventually switch to support 32-bit PV guests only via PV-shim from >> Xen 4.12 or 4.13 >> >> - dropping 32-bit PV support from upstream Linux kernel, resulting in >> current 32-bit PV guests no longer being able to upgrade to the newest >> kernel version any longer >> >> And related to that: >> >> - is there any Linux distribution still shipping 32-bit PV-capable >> systems? >> >> - what about BSD? Is 32-bit PV support important there? >> > > > Juergen - just to be very clear about the scope here: > * would this proposal affect the ability to use a 32-bit dom0? If the Dom0 is to be PV - yes, of course. For the time being there's no complete PVH Dom0 support, so if 32-bit is needed here, PV is for now indeed the only option. > * is this proposal to affect x86 only or also for ARM? There's no PV on ARM. Jan ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
>>> On 16.08.18 at 08:17, wrote: > In the Xen x86 community call we have been discussing whether anyone > really is depending on 32-bit PV guests. We'd like to evaluate whether > anyone would see problems with: > > - deprecating 32-bit PV guest support in Xen, meaning that we'd > eventually switch to support 32-bit PV guests only via PV-shim from > Xen 4.12 or 4.13 I think we shouldn't try to be too eager here. Deprecating is fine if we can get sufficient confirmation that no-one needs this anymore, but switching to something like the shim-only model needs to come sufficiently much later. For people concerned about memory footprint, should we perhaps make x32 support in public headers and tool stack a prereq here? Not the least because - afaict - 32-bit user space support in 64-bit Linux continues to be subtly broken, due to there not being any clear route for what to do with "x86-64/Xen: fix stack switching", sent over three months ago? But even without that I think x32 is preferable over true 32-bit mode. Jan > - dropping 32-bit PV support from upstream Linux kernel, resulting in > current 32-bit PV guests no longer being able to upgrade to the newest > kernel version any longer > > And related to that: > > - is there any Linux distribution still shipping 32-bit PV-capable > systems? > > - what about BSD? Is 32-bit PV support important there? > > > Juergen > > ___ > Xen-devel mailing list > Xen-devel@lists.xenproject.org > https://lists.xenproject.org/mailman/listinfo/xen-devel ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] Future of 32-bit PV support
On Wed, Aug 15, 2018 at 11:17 PM, Juergen Gross wrote: > In the Xen x86 community call we have been discussing whether anyone > really is depending on 32-bit PV guests. We'd like to evaluate whether > anyone would see problems with: > > - deprecating 32-bit PV guest support in Xen, meaning that we'd > eventually switch to support 32-bit PV guests only via PV-shim from > Xen 4.12 or 4.13 > > - dropping 32-bit PV support from upstream Linux kernel, resulting in > current 32-bit PV guests no longer being able to upgrade to the newest > kernel version any longer > > And related to that: > > - is there any Linux distribution still shipping 32-bit PV-capable > systems? > > - what about BSD? Is 32-bit PV support important there? > Juergen - just to be very clear about the scope here: * would this proposal affect the ability to use a 32-bit dom0? * is this proposal to affect x86 only or also for ARM? Christopher ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
