Re: [Xen-devel] [RFC] arm: Handle SiP Service Calls

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hello,

On 07/12/17 06:48, Peng Fan wrote:
> Support ARM SiP (Silicon Provider) services.
>   - Import arm-smccc.h from Linux Kernel
>     ca122fe376fc ("Merge tag 'arc-4.15-rc1' of
>     git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc")
>   - Introudce a new callback function in platform_desc
>   - Add do_trap_hvccc to handle non xen specific hypercalls
>
>   Platforms that want to use SiP service could use platform
>   specific sip implementation.
It looks like to me that this patch is based on an older version of Xen. 
3 months ago, a framework to support SMC Calling Convention for guest 
was added.
In general, patch sent upstream should be based on latest Xen. So please 
rebase your code.
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> ---
>
> In my Dom0 kernel, there is SiP smccc call. Without xen, the call
> will trap to ATF. With xen, I use hvccc to replace smccc, but
> xen still report error, because xen does not handle SiP calls.
> Not sure this is the best way. Since SiP is silicon provider
> service, so I put it into platform code.
When I see a new callback added, I would expect to see a user in the 
series. So what is the expected behavior of this callback? Who is going 
to be allowed to access to the SiP services?
Guessing from your description, the callback would just be implemented 
as "forward SiP call". In that case, I don't see a reason to have a 
callback implemented.
However, you would need to know whether the platform support SMCCC. How 
do you recognize that on yours?
Now the next question, is it safe to let the hardware domain to access 
all SiP service? Can you explain the kind of service present in SiP for 
your platform?
Cheers,

--
Julien Grall

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