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Re: [PATCH v2 7/7] xen/arm: introduce new xen,enhanced property value
- To: Julien Grall <julien@xxxxxxx>
- From: Rahul Singh <Rahul.Singh@xxxxxxx>
- Date: Wed, 24 Aug 2022 16:35:48 +0000
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- Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Wed, 24 Aug 2022 16:36:31 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH v2 7/7] xen/arm: introduce new xen,enhanced property value
Hi Julien
> On 24 Aug 2022, at 4:36 pm, Julien Grall <julien@xxxxxxx> wrote:
>
> On 24/08/2022 15:42, Rahul Singh wrote:
>>> On 24 Aug 2022, at 1:59 pm, Julien Grall <julien@xxxxxxx> wrote:
>>>
>>>
>>>
>>> On 24/08/2022 13:15, Rahul Singh wrote:
>>>> Hi Julien,
>>>
>>> Hi Rahul,
>>>
>>>> Please let me know your view on this.
>>>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>>>> index bfe7bc6b36..a1e23eee59 100644
>>>> --- a/xen/arch/arm/domain_build.c
>>>> +++ b/xen/arch/arm/domain_build.c
>>>> @@ -3562,12 +3562,7 @@ static int __init construct_domU(struct domain *d,
>>>> if ( rc == -EILSEQ ||
>>>> rc == -ENODATA ||
>>>> (rc == 0 && !strcmp(dom0less_enhanced, “enabled”)) )
>>>> - {
>>>> - if ( hardware_domain )
>>>> kinfo.dom0less_enhanced = true;
>>>> - else
>>>> - panic(“Tried to use xen,enhanced without dom0\n”);
>>>> - }
>>>
>>> You can't use "xen,enhanced" without dom0. In fact, you will end up to
>>> dereference NULL in alloc_xenstore_evtchn(). That's because "xen,enhanced"
>>> means the domain will be able to use Xenstored.
>>>
>>> Now if you want to support your feature without a dom0. Then I think we
>>> want to introduce an option which would be the same as "xen,enhanced" but
>>> doesn't expose Xenstored.
>> If we modify the patch as below we can use the "xen,enhanced" for domUs
>> without dom0.
>> I tested the patch and its works fine. Do you see any issue with this
>> approach?
>
> Yes. For two reasons:
> 1) It is muddying the meaning of "xen,enhanced". In particular a user may not
> realize that Xenstore is not available if dom0 is not present.
> 2) It would be more complicated to handle the case where Xenstored lives in a
> non-dom0 domain. I am not aware of anyone wanting this on Arm yet, but I
> don't want to close the door.
>
> So if you want to support create "xen,xen" without all the rest. Then I think
> we need a different property value. I don't have a good suggestion for the
> name.
Is that okay if we use the earlier approach, when user set "xen,enhanced =
evtchn” we will not call alloc_xenstore_evtchn()
but we create hypervisor node with all fields.
Regards,
Rahul
|
