dom0=pvh and 4.18

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dom0=pvh and 4.18

Glenn Enright
Hi all,

Doing some testing with 4.18 kernel, trying to get dom0=pvh working with
xen4.11.

Builds are from my own test machine, with a gcc8.0 toolchain for
centos6. Test machine is a Supermicro X9 board with Dual E52630v2 cpus.

What I'm seeing is that xen boots up fine, but on the transition to the
linux kernel, the screen goes blank and the server never pings. I've
tried a bunch of different command line options including various
console/serial with no change.

Does anyone have a magical set of xen boot options that could help get
me started or at least show something to point the way?

Thanks
--Glenn

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Fwd: dom0=pvh and 4.18

Paul Gorman
On Sun, Aug 12, 2018, 8:32 PM Glenn Enright <[hidden email]> wrote:
Hi all,

Doing some testing with 4.18 kernel, trying to get dom0=pvh working with
xen4.11.

Builds are from my own test machine, with a gcc8.0 toolchain for
centos6. Test machine is a Supermicro X9 board with Dual E52630v2 cpus.

What I'm seeing is that xen boots up fine, but on the transition to the
linux kernel, the screen goes blank and the server never pings. I've
tried a bunch of different command line options including various
console/serial with no change.

Does anyone have a magical set of xen boot options that could help get
me started or at least show something to point the way?

Thanks
--Glenn

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Glenn! I had some issues getting Dom0 to boot up as well. My initramfs requires a password entry, and such was not allowed by my initial setup. I feel your pain.

Lemme share what got me off the ground, in case it has something you haven't tried.

In the grub.cfg:

multiboot    /xen.gz dom0_mem=2048M.max:4096M iommu=no-igfx ucode=scan

module /vm-linuz-4.17.13-gentoo {stuff specific to my setup that I doubt we have in common} softlevel=xen console=tty quiet vt.handoff=3 

The "console=tty" was important for me. And vt.handoff=3 for a console-booting system. vt.handoff=7 if it boots directly into a DE.

And now you've got me curious about how to replicate your success. Where is the Dom0 config file where I can add "type=pvh"? Was there more involved than what you've already mentioned?

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Re: dom0=pvh and 4.18

Christoph Kaminski
In reply to this post by Glenn Enright
Hi,

what are the advantages of a pvh dom0?

Am 2018-08-13 02:31, schrieb Glenn Enright:

> Hi all,
>
> Doing some testing with 4.18 kernel, trying to get dom0=pvh working
> with xen4.11.
>
> Builds are from my own test machine, with a gcc8.0 toolchain for
> centos6. Test machine is a Supermicro X9 board with Dual E52630v2
> cpus.
>
> What I'm seeing is that xen boots up fine, but on the transition to
> the linux kernel, the screen goes blank and the server never pings.
> I've tried a bunch of different command line options including various
> console/serial with no change.
>
> Does anyone have a magical set of xen boot options that could help get
> me started or at least show something to point the way?
>
> Thanks
> --Glenn
>
> _______________________________________________
> Xen-users mailing list
> [hidden email]
> https://lists.xenproject.org/mailman/listinfo/xen-users

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Re: dom0=pvh and 4.18

Glenn Enright
HI there

A I understand it, pvh is faster, and it also has the benefit of not
using qemu, so code is much simpler.

https://www.serverwatch.com/server-news/xen-4.11-improves-server-virtualization-with-pvh.html

Regards, Glenn
http://ri.mu - Startups start here.
Hosting, Email, DNS, Offsite Backups, Monitoring.

On 13/08/18 19:22, Christoph wrote:

> Hi,
>
> what are the advantages of a pvh dom0?
>
> Am 2018-08-13 02:31, schrieb Glenn Enright:
>> Hi all,
>>
>> Doing some testing with 4.18 kernel, trying to get dom0=pvh working
>> with xen4.11.
>>
>> Builds are from my own test machine, with a gcc8.0 toolchain for
>> centos6. Test machine is a Supermicro X9 board with Dual E52630v2
>> cpus.
>>
>> What I'm seeing is that xen boots up fine, but on the transition to
>> the linux kernel, the screen goes blank and the server never pings.
>> I've tried a bunch of different command line options including various
>> console/serial with no change.
>>
>> Does anyone have a magical set of xen boot options that could help get
>> me started or at least show something to point the way?
>>
>> Thanks
>> --Glenn
>>
>> _______________________________________________
>> Xen-users mailing list
>> [hidden email]
>> https://lists.xenproject.org/mailman/listinfo/xen-users
>

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Re: Fwd: dom0=pvh and 4.18

Glenn Enright
In reply to this post by Paul Gorman
On 13/08/18 14:51, Paul Gorman wrote:

> On Sun, Aug 12, 2018, 8:32 PM Glenn Enright <[hidden email]> wrote:
>
>> Hi all,
>>
>> Doing some testing with 4.18 kernel, trying to get dom0=pvh working with
>> xen4.11.
>>
>> Builds are from my own test machine, with a gcc8.0 toolchain for
>> centos6. Test machine is a Supermicro X9 board with Dual E52630v2 cpus.
>>
>> What I'm seeing is that xen boots up fine, but on the transition to the
>> linux kernel, the screen goes blank and the server never pings. I've
>> tried a bunch of different command line options including various
>> console/serial with no change.
>>
>> Does anyone have a magical set of xen boot options that could help get
>> me started or at least show something to point the way?
>>
>> Thanks
>> --Glenn
>>
>
> Glenn! I had some issues getting Dom0 to boot up as well. My initramfs
> requires a password entry, and such was not allowed by my initial setup. I
> feel your pain.
>
> Lemme share what got me off the ground, in case it has something you
> haven't tried.
>
> In the grub.cfg:
>
> multiboot    /xen.gz dom0_mem=2048M.max:4096M iommu=no-igfx ucode=scan
>
> module /vm-linuz-4.17.13-gentoo {stuff specific to my setup that I doubt we
> have in common} softlevel=xen console=tty quiet vt.handoff=3
>
> The "console=tty" was important for me. And vt.handoff=3 for a
> console-booting system. vt.handoff=7 if it boots directly into a DE.
>
> And now you've got me curious about how to replicate your success. Where is
> the Dom0 config file where I can add "type=pvh"? Was there more involved
> than what you've already mentioned?
>

FWIW dom0=pvh is a xen command line option. It is new/experimental.

The point is I never to get a pinging dom0. So not succeeding at all.
All that is seen is a blank screen after the hyper-visor hands off to
the kernel. A stripped down example set of grub looks like below. Note
no quiet or rhgb options.

kernel /xen.gz dom0_mem=2048M iommu=required,debug,verbose dom0=pvh
module /vmlinuz-4.18.0-2.el6xen.x86_64 ro root=<sniped> pcie_aspm=off
panic=30
module /initrd-4.18.0-2.el6xen.x86_64.img

So my question, restated, are there any gotchas in getting dom0 booting
specifically in pvh mode?

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Re: dom0=pvh and 4.18

Christoph Kaminski
In reply to this post by Glenn Enright
Hi,

would it be possible to boot dom0 without booting of the whole host?

Am 2018-08-14 01:31, schrieb Glenn Enright:

> HI there
>
> A I understand it, pvh is faster, and it also has the benefit of not
> using qemu, so code is much simpler.
>
> https://www.serverwatch.com/server-news/xen-4.11-improves-server-virtualization-with-pvh.html
>
> Regards, Glenn
> http://ri.mu - Startups start here.
> Hosting, Email, DNS, Offsite Backups, Monitoring.
>
> On 13/08/18 19:22, Christoph wrote:
>> Hi,
>>
>> what are the advantages of a pvh dom0?
>>
>> Am 2018-08-13 02:31, schrieb Glenn Enright:
>>> Hi all,
>>>
>>> Doing some testing with 4.18 kernel, trying to get dom0=pvh working
>>> with xen4.11.
>>>
>>> Builds are from my own test machine, with a gcc8.0 toolchain for
>>> centos6. Test machine is a Supermicro X9 board with Dual E52630v2
>>> cpus.
>>>
>>> What I'm seeing is that xen boots up fine, but on the transition to
>>> the linux kernel, the screen goes blank and the server never pings.
>>> I've tried a bunch of different command line options including
>>> various
>>> console/serial with no change.
>>>
>>> Does anyone have a magical set of xen boot options that could help
>>> get
>>> me started or at least show something to point the way?
>>>
>>> Thanks
>>> --Glenn
>>>
>>> _______________________________________________
>>> Xen-users mailing list
>>> [hidden email]
>>> https://lists.xenproject.org/mailman/listinfo/xen-users
>>

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Re: dom0=pvh and 4.18

Juergen Gross-3
In reply to this post by Glenn Enright
On 14/08/18 01:31, Glenn Enright wrote:
> HI there
>
> A I understand it, pvh is faster, and it also has the benefit of not
> using qemu, so code is much simpler.

The main advantage of PVH is a much simpler interface between guest
(in this case dom0) and the hypervisor. This is reducing the attack
surface of the whole system. Another advantage is that the guest doesn't
need to support the PV interface, which is rather intrusive in the guest
OS.

PVH is faster for some workloads, for others PV is faster. Especially
for dom0 there are still some known performance issues when running
in PVH mode, e.g. for domain creation and backend functionality.

Not using qemu is true for PV, too. And dom0 can't make use of qemu, of
course, as there is no instance qemu could run in when dom0 is booting.


Juergen

>
> https://www.serverwatch.com/server-news/xen-4.11-improves-server-virtualization-with-pvh.html
>
> Regards, Glenn
> http://ri.mu - Startups start here.
> Hosting, Email, DNS, Offsite Backups, Monitoring.
>
> On 13/08/18 19:22, Christoph wrote:
>> Hi,
>>
>> what are the advantages of a pvh dom0?
>>
>> Am 2018-08-13 02:31, schrieb Glenn Enright:
>>> Hi all,
>>>
>>> Doing some testing with 4.18 kernel, trying to get dom0=pvh working
>>> with xen4.11.
>>>
>>> Builds are from my own test machine, with a gcc8.0 toolchain for
>>> centos6. Test machine is a Supermicro X9 board with Dual E52630v2
>>> cpus.
>>>
>>> What I'm seeing is that xen boots up fine, but on the transition to
>>> the linux kernel, the screen goes blank and the server never pings.
>>> I've tried a bunch of different command line options including various
>>> console/serial with no change.
>>>
>>> Does anyone have a magical set of xen boot options that could help get
>>> me started or at least show something to point the way?
>>>
>>> Thanks
>>> --Glenn
>>>
>>> _______________________________________________
>>> Xen-users mailing list
>>> [hidden email]
>>> https://lists.xenproject.org/mailman/listinfo/xen-users
>>
>
> _______________________________________________
> Xen-users mailing list
> [hidden email]
> https://lists.xenproject.org/mailman/listinfo/xen-users
>


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Re: dom0=pvh and 4.18

peter-4
On 14/08/18 5:23 PM, Juergen Gross wrote:

> On 14/08/18 01:31, Glenn Enright wrote:
>> HI there
>>
>> A I understand it, pvh is faster, and it also has the benefit of not
>> using qemu, so code is much simpler.
> The main advantage of PVH is a much simpler interface between guest
> (in this case dom0) and the hypervisor. This is reducing the attack
> surface of the whole system. Another advantage is that the guest doesn't
> need to support the PV interface, which is rather intrusive in the guest
> OS.
>
> PVH is faster for some workloads, for others PV is faster. Especially
> for dom0 there are still some known performance issues when running
> in PVH mode, e.g. for domain creation and backend functionality.
>
> Not using qemu is true for PV, too. And dom0 can't make use of qemu, of
> course, as there is no instance qemu could run in when dom0 is booting.
>
>
> Juergen
>
Is there a page that describes how to boot dom0 as PVH?  With any
pre-requisites (e.g. latest 4.18 linux kernel) and example grub boot
lines.  The feature is listed as 'experimental'.  Should we expect dom0
to start up (since it is not booting per Glenn's message).  Are there
known issues?

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Re: dom0=pvh and 4.18

Juergen Gross-3
On 15/08/18 01:49, [hidden email] wrote:

> On 14/08/18 5:23 PM, Juergen Gross wrote:
>> On 14/08/18 01:31, Glenn Enright wrote:
>>> HI there
>>>
>>> A I understand it, pvh is faster, and it also has the benefit of not
>>> using qemu, so code is much simpler.
>> The main advantage of PVH is a much simpler interface between guest
>> (in this case dom0) and the hypervisor. This is reducing the attack
>> surface of the whole system. Another advantage is that the guest doesn't
>> need to support the PV interface, which is rather intrusive in the guest
>> OS.
>>
>> PVH is faster for some workloads, for others PV is faster. Especially
>> for dom0 there are still some known performance issues when running
>> in PVH mode, e.g. for domain creation and backend functionality.
>>
>> Not using qemu is true for PV, too. And dom0 can't make use of qemu, of
>> course, as there is no instance qemu could run in when dom0 is booting.
>>
>>
>> Juergen
>>
> Is there a page that describes how to boot dom0 as PVH?  With any
> pre-requisites (e.g. latest 4.18 linux kernel) and example grub boot
> lines.  The feature is listed as 'experimental'.  Should we expect dom0
> to start up (since it is not booting per Glenn's message).  Are there
> known issues?

Xen support is experimental. Linux support is still being worked at.


Juergen

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Re: dom0=pvh and 4.18

Roger Pau Monné-3
In reply to this post by Glenn Enright
On Mon, Aug 13, 2018 at 12:31:26PM +1200, Glenn Enright wrote:

> Hi all,
>
> Doing some testing with 4.18 kernel, trying to get dom0=pvh working with
> xen4.11.
>
> Builds are from my own test machine, with a gcc8.0 toolchain for centos6.
> Test machine is a Supermicro X9 board with Dual E52630v2 cpus.
>
> What I'm seeing is that xen boots up fine, but on the transition to the
> linux kernel, the screen goes blank and the server never pings. I've tried a
> bunch of different command line options including various console/serial
> with no change.
>
> Does anyone have a magical set of xen boot options that could help get me
> started or at least show something to point the way?

Thanks for the testing!

You will have to setup a serial console in order to get the output
from Xen and early Linux boot, without that it's going to be almost
impossible to debug any issues.

That aside, in order to test PVH Dom0 you will have to use the xen.git
staging branch. Xen 4.11 is still missing some required patches for
Dom0 support which are now committed to staging.

If you build 4.11 by yourself building staging should be no different.
If you still see issues with staging, please paste the full serial
log of Xen + Dom0 booting.

Roger.

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