Re: [Xen-devel] [RFC v2 3/6] xen/arm: Allow platform_hvc to handle guest SMC calls

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Thu, Feb 9, 2017 at 11:39 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
> Hi Tamas,
>
> On 02/09/2017 06:11 PM, Tamas K Lengyel wrote:
>>
>> On Wed, Feb 8, 2017 at 5:08 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>>>
>>> On 08/02/2017 23:28, Tamas K Lengyel wrote:
>>>>
>>>> On Wed, Feb 8, 2017 at 3:04 PM, Julien Grall <julien.grall@xxxxxxx>
>>>> wrote:
>>>
>>> You haven't understood my point. Xen is currently emulating PSCI call for
>>> the guest to allow powering up and down the CPUs and other stuff. If you
>>> decide to trap all the SMCs, you would have to handle them.
>>
>>
>> Sure, it's more work on the monitor side, but other then that, what's
>> the problem?
>
>
> Because you will have to introduce hypercalls to get all the necessary
> information from Xen that will not be available from outside.
>
> Given that SMC has been designed to target different services (PSCI, Trusted
> OS...) it would be normal to have monitor app only monitoring a certain set
> of SMC call. You cannot deny a such use case as it would avoid an monitor
> app to handle every single call that would be consumed by XEN but not
> forwarded to the secure firmware.
>

I have nothing against introducing a fine-tune option to the SMC
monitoring system so the monitor app can determine if it wants all
SMCs or only a subset. At the moment I don't know of any usecase that
would require this option. I certainly don't need it. If this option
gets implemented by someone, I would be happy to take it.

Tamas

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