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

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

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 <boris.ostrovsky@xxxxxxxxxx>
>> ---
>>  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 B<pvh=BOOLEAN>
>> +
>> +Don't use any device model. This requires a kernel capable of booting
>> +without emulated devices. Default is 0.
>> +
>>  =item B<shadow_memory=MBYTES>
>>  
>>  Number of megabytes to set aside for shadowing guest pagetable pages
>> @@ -1966,7 +1971,7 @@ This device-model is still the default for NetBSD dom0.
>>  =item B<none>
>>  
>>  Don't use any device model. This requires a kernel capable of booting
>> -without emulated devices.
>> +without emulated devices. This is a synonym for L</"pvh"> option above.
>>  
>>  =back
>>  
>> diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
>> index 66327dc..aa591cd 100644
>> --- a/tools/xl/xl_parse.c
>> +++ b/tools/xl/xl_parse.c
>> @@ -1817,6 +1817,12 @@ skip_usbdev:
>>          break;
>>      }
>>  
>> +    if (c_info->type == LIBXL_DOMAIN_TYPE_HVM &&
> Hm, this will mean that the user needs to specify:
>
> builder="hvm"
> pvh=1
>
> Or else the option is not going to be parsed.

Right. I've always had builder directive in my config file so I didn't
think of that. I'll remove the check.

-boris

>
>> +        !xlu_cfg_get_long(config, "pvh", &l, 0) && l) {
>> +        b_info->device_model_version = LIBXL_DEVICE_MODEL_VERSION_NONE;
>> +        goto skip_device_model;
>> +    }
>> +
> Roger.


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