Re: [Xen-devel] [PATCH v4] vm_event: Implement ARM SMC events

[Julien Grall <julien.grall@xxxxxxx>]

Hi Tamas,

On 16/09/2016 10:43, Tamas K Lengyel wrote:
> The ARM SMC instructions are already configured to trap to Xen by default. In
> this patch we allow a user-space process in a privileged domain to receive
> notification of when such event happens through the vm_event subsystem by
> introducing the PRIVILEGED_CALL type.
>
> The intended use-case for this feature is for a monitor application to be able
> insert tap-points into the domU kernel-code. For this task only unconditional
> SMC instruction should be used.
>
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> Acked-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> ---
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>
>
> v4: Style fixes
>
> Note: previous discussion around this patch proposed filtering SMCs with failed
>       condition checks. As that patch is yet-to-be implemented and the 4.8
>       code-freeze rapidly approaching I would like this patch to get included.
>       In this patch a proper warning is placed in the public header for
>       potential users not to rely on SMCs with failed condition checks being
>       trapped. As the intended use-case for this feature doesn't use
>       conditional SMCs this warning should be sufficient. Hardware that does
>       issue events for SMCs with failed condition checks doesn't pose a problem
>       for a monitor application in any way. The xen-access test tool illustrates
>       how SMCs issued by the guest can be safely handled for all cases.
I will let Stefano decides whether we should include this patch as it in 
Xen 4.8.
Regards,

--
Julien Grall

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