Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Boris Ostrovsky]

On 03/31/2017 10:33 AM, Ian Jackson wrote:
> Roger Pau Monné writes ("Re: [PATCH] xl: Add 'pvh' config option"):
>> On Fri, Mar 31, 2017 at 09:59:09AM -0400, Boris Ostrovsky wrote:
>>> That would make the toolstack have three guest types while the
>>> hypervisor has two.
> Is that a problem, conceptually ?  It seems to me to be accurate here.

To my eyes --- yes. Guest type is a basic concept and having toolstack
and the hypervisor disagree on how many guest types exist doesn't sound
right.

This doesn't mean that there shouldn't indeed be 3 types --- I agree
that from admin perspective PVH is nothing like HVM.

There is also another question, BTW: since PVH(v2) will first appear in
4.9 it would be nice to provide user-visible config options (i.e. 'pvh'
instead of or in addition to 'device_model_version=none') before
release, even if (proper) implementation is still under discussion.  But
perhaps the train has left the station already.

-boris

>
>> This was discussed on the PVHv1 removal patches. I sent a PVHv1 removal that
>> partially covered this (by adding a PVH guest type to libxl), but IMHO I find
>> it quite hard to add a guest type to libxl only (when it's not on the
>> hypervisor).
>>
>> It can certainly be done, but it's painful due to libxl having to filter the
>> output from Xen in order to properly detect guest types, since it cannot 
>> longer
>> use Xen values blindly.
> How many places in libxl have to change ?
>


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Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Ian Jackson]

Roger Pau Monné writes ("Re: [PATCH] xl: Add 'pvh' config option"):
> On Fri, Mar 31, 2017 at 09:59:09AM -0400, Boris Ostrovsky wrote:
> > That would make the toolstack have three guest types while the
> > hypervisor has two.

Is that a problem, conceptually ?  It seems to me to be accurate here.

> This was discussed on the PVHv1 removal patches. I sent a PVHv1 removal that
> partially covered this (by adding a PVH guest type to libxl), but IMHO I find
> it quite hard to add a guest type to libxl only (when it's not on the
> hypervisor).
> 
> It can certainly be done, but it's painful due to libxl having to filter the
> output from Xen in order to properly detect guest types, since it cannot 
> longer
> use Xen values blindly.

How many places in libxl have to change ?

Ian.

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Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Roger Pau Monné]

On Fri, Mar 31, 2017 at 09:59:09AM -0400, Boris Ostrovsky wrote:
> On 03/31/2017 09:49 AM, Wei Liu wrote:
> > On Fri, Mar 31, 2017 at 09:43:07AM -0400, Boris Ostrovsky wrote:
> >> On 03/31/2017 06:23 AM, Roger Pau Monné wrote:
> >>> On Thu, Mar 30, 2017 at 07:06:15PM -0400, Boris Ostrovsky wrote:
>  In addition to 'device_model_version="none"' config option users can
>  also use 'pvh=1' in xl configuration file when creating a PVH guest.
> >>> I'm not sure, but I think the plan was to remove 
> >>> device_model_version="none"
> >>> and instead just use pvh=1, instead of keeping both. I don't have a strong
> >>> opinion here, so I will leave that to the xl maintainers.
> >> I thought we had PVHv2 in 4.8 but apparently not. I will remove it then.
> >>
> > You can't remove the DM version none just yet.
> >
> > I think Ian has ask for adding a PVH guest type and pvh=1 sets that. It
> > is a bit more work than this patch.
> 
> That would make the toolstack have three guest types while the
> hypervisor has two.
> 
> (Maybe this was already covered but I don't remember seeing this
> discussion).

This was discussed on the PVHv1 removal patches. I sent a PVHv1 removal that
partially covered this (by adding a PVH guest type to libxl), but IMHO I find
it quite hard to add a guest type to libxl only (when it's not on the
hypervisor).

It can certainly be done, but it's painful due to libxl having to filter the
output from Xen in order to properly detect guest types, since it cannot longer
use Xen values blindly.

Roger.

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Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Wei Liu]

On Fri, Mar 31, 2017 at 09:59:09AM -0400, Boris Ostrovsky wrote:
> On 03/31/2017 09:49 AM, Wei Liu wrote:
> > On Fri, Mar 31, 2017 at 09:43:07AM -0400, Boris Ostrovsky wrote:
> >> On 03/31/2017 06:23 AM, Roger Pau Monné wrote:
> >>> On Thu, Mar 30, 2017 at 07:06:15PM -0400, Boris Ostrovsky wrote:
>  In addition to 'device_model_version="none"' config option users can
>  also use 'pvh=1' in xl configuration file when creating a PVH guest.
> >>> I'm not sure, but I think the plan was to remove 
> >>> device_model_version="none"
> >>> and instead just use pvh=1, instead of keeping both. I don't have a strong
> >>> opinion here, so I will leave that to the xl maintainers.
> >> I thought we had PVHv2 in 4.8 but apparently not. I will remove it then.
> >>
> > You can't remove the DM version none just yet.
> >
> > I think Ian has ask for adding a PVH guest type and pvh=1 sets that. It
> > is a bit more work than this patch.
> 
> That would make the toolstack have three guest types while the
> hypervisor has two.
> 

Correct.

> (Maybe this was already covered but I don't remember seeing this
> discussion).
> 

See: <22709.46867.434595.470...@mariner.uk.xensource.com>

> -boris
> 

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Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Wei Liu]

On Fri, Mar 31, 2017 at 09:43:07AM -0400, Boris Ostrovsky wrote:
> On 03/31/2017 06:23 AM, Roger Pau Monné wrote:
> > On Thu, Mar 30, 2017 at 07:06:15PM -0400, Boris Ostrovsky wrote:
> >> In addition to 'device_model_version="none"' config option users can
> >> also use 'pvh=1' in xl configuration file when creating a PVH guest.
> > I'm not sure, but I think the plan was to remove device_model_version="none"
> > and instead just use pvh=1, instead of keeping both. I don't have a strong
> > opinion here, so I will leave that to the xl maintainers.
> 
> I thought we had PVHv2 in 4.8 but apparently not. I will remove it then.
> 

You can't remove the DM version none just yet.

I think Ian has ask for adding a PVH guest type and pvh=1 sets that. It
is a bit more work than this patch.

Wei.

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Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Boris Ostrovsky]

On 03/31/2017 06:23 AM, Roger Pau Monné wrote:
> On Thu, Mar 30, 2017 at 07:06:15PM -0400, Boris Ostrovsky wrote:
>> In addition to 'device_model_version="none"' config option users can
>> also use 'pvh=1' in xl configuration file when creating a PVH guest.
> I'm not sure, but I think the plan was to remove device_model_version="none"
> and instead just use pvh=1, instead of keeping both. I don't have a strong
> opinion here, so I will leave that to the xl maintainers.

I thought we had PVHv2 in 4.8 but apparently not. I will remove it then.

>
> I'm also not sure, but if you use device_model_version="none" can you use 
> QDISK
> for PVH disk backend? (and pygrub).

We are not starting qemu so I don't think I see how we can use qdisk
(unless you are suggesting that we should do that for qdisk specifically).

Not sure what you are asking for pygrub.

>
>> We can skip parsing options related to device model once we establish
>> that we are building PVH guest.
>>
>> Also process 'device_model_version="none"' for HVM guests only since
>> it is not a valid model for PV guests.
>>
>> Signed-off-by: Boris Ostrovsky 
>> ---
>>  docs/man/xl.cfg.pod.5.in |  7 ++-
>>  tools/xl/xl_parse.c  | 12 +++-
>>  2 files changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
>> index 206d33e..5833987 100644
>> --- a/docs/man/xl.cfg.pod.5.in
>> +++ b/docs/man/xl.cfg.pod.5.in
>> @@ -1201,6 +1201,11 @@ expose unexpected bugs in the guest, or find bugs in 
>> Xen, so it is
>>  possible to disable this feature.  Use of out of sync page tables,
>>  when Xen thinks it appropriate, is the default.
>>  
>> +=item 

Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Wei Liu]

On Fri, Mar 31, 2017 at 11:23:04AM +0100, Roger Pau Monné wrote:
> On Thu, Mar 30, 2017 at 07:06:15PM -0400, Boris Ostrovsky wrote:
> > In addition to 'device_model_version="none"' config option users can
> > also use 'pvh=1' in xl configuration file when creating a PVH guest.
> 
> I'm not sure, but I think the plan was to remove device_model_version="none"
> and instead just use pvh=1, instead of keeping both. I don't have a strong
> opinion here, so I will leave that to the xl maintainers.
> 

Yes, that's the plan.

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Re: [Xen-devel] [PATCH] xl: Add 'pvh' config option

[Roger Pau Monné]

On Thu, Mar 30, 2017 at 07:06:15PM -0400, Boris Ostrovsky wrote:
> In addition to 'device_model_version="none"' config option users can
> also use 'pvh=1' in xl configuration file when creating a PVH guest.

I'm not sure, but I think the plan was to remove device_model_version="none"
and instead just use pvh=1, instead of keeping both. I don't have a strong
opinion here, so I will leave that to the xl maintainers.

I'm also not sure, but if you use device_model_version="none" can you use QDISK
for PVH disk backend? (and pygrub).

> We can skip parsing options related to device model once we establish
> that we are building PVH guest.
> 
> Also process 'device_model_version="none"' for HVM guests only since
> it is not a valid model for PV guests.
> 
> Signed-off-by: Boris Ostrovsky 
> ---
>  docs/man/xl.cfg.pod.5.in |  7 ++-
>  tools/xl/xl_parse.c  | 12 +++-
>  2 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
> index 206d33e..5833987 100644
> --- a/docs/man/xl.cfg.pod.5.in
> +++ b/docs/man/xl.cfg.pod.5.in
> @@ -1201,6 +1201,11 @@ expose unexpected bugs in the guest, or find bugs in 
> Xen, so it is
>  possible to disable this feature.  Use of out of sync page tables,
>  when Xen thinks it appropriate, is the default.
>  
> +=item 

[Xen-devel] [PATCH] xl: Add 'pvh' config option

[Boris Ostrovsky]

In addition to 'device_model_version="none"' config option users can
also use 'pvh=1' in xl configuration file when creating a PVH guest.

We can skip parsing options related to device model once we establish
that we are building PVH guest.

Also process 'device_model_version="none"' for HVM guests only since
it is not a valid model for PV guests.

Signed-off-by: Boris Ostrovsky 
---
 docs/man/xl.cfg.pod.5.in |  7 ++-
 tools/xl/xl_parse.c  | 12 +++-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
index 206d33e..5833987 100644
--- a/docs/man/xl.cfg.pod.5.in
+++ b/docs/man/xl.cfg.pod.5.in
@@ -1201,6 +1201,11 @@ expose unexpected bugs in the guest, or find bugs in 
Xen, so it is
 possible to disable this feature.  Use of out of sync page tables,
 when Xen thinks it appropriate, is the default.
 
+=item