[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

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.


Julien Grall

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.