Re: [Xen-users] Got permission denied error when calling xenbus_printf function in the frontend driver

[Jintack Lim <jintack@xxxxxxxxxxxxxxx>]

On Tue, Aug 4, 2015 at 7:15 AM, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> On Tue, 2015-08-04 at 07:07 -0400, Jintack Lim wrote:
>> After I added a few lines to give read/write permission of some keys to
>> domU,
>> then "permission denied" error was gone, and the driver worked fine.
>
> Great!

Thanks!

I got one more question.
I wonder if the backend/frontend driver on PV are supposed to work
well on HVM as well.

My backend/frontend driver worked well on ARM64 PV domains.
However, when I ran the same driver on x86 PV driver domain and HVM
guest domain(PVHVM),
I got a kernel panic in the backend driver as soon as I fired the
probe function in the backend.
More specifically, it's when the backend driver tries to send a
notification through
evtchn_from_irq() function.

>
>> They look like this.
>>
>> xenstore-chmod /local/domain/${2}/device/${1}/0/state b
>> xenstore-chmod /local/domain/${2}/device/${1}/0/ring-ref b
>> xenstore-chmod /local/domain/${2}/device/${1}/0/event-channel b
>
> I think that has likely given r/w access to all domains, probably OK if you
> are just benchmarking but don't deploy this :-)
>
> "n${2} r0" AKA owned by the frontend, read-only for the backend (hardcoded
> as dom0 here) might be more appropriate in real life.
>

Wow,, that's nice!

Jintack


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