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

Re: [Xen-devel] [PATCH v5 12/22] xen/arm: ITS: Add GICR register emulation

On 04/08/2015 07:55, Vijay Kilari wrote:

What would happen if the LPI is injected before the GICR_PROPBASER is
enabled? See for more details on the problem here [1]

  Check is required before accessing LPI property table if property
table is available
or not?.

You didn't answer to my question... What would you do if the property is
not available? Ignoring the LPI? Would the LPI can fire back after the
property table is set and the LPI enabled?

    Same as above solution.  Ignore LPI as we don't have LPI property
information to inject.

That still not answering to my question. What happen if we ignore the
LPI? Would the device resend the MSI and therefore the LPI later? If
not, how do you plan to handle this?

   LPIs are edge triggered, so device won't raise again.

We can put in inflight and wait for guest to enabled it, But we are not sure
when LPI property table will be set for this vLPI. On GICR_PROPBASER update
with new property table, we parse the LPI property table and call

If we don't put it inflight, we will surely loose some interrupt at some point if the device is not quiet before the guest has booted and/or setup the device before enabling the LPI.

With the LPI implementation, it's valid to receive an LPI before the
guest effectively setup the ITS (i.e property table and the mapping to a
vLPI). This is because we enable to LPI as soon as we route it to the guest.


Julien Grall

[1] http://lists.xenproject.org/archives/html/xen-devel/2015-06/msg02591.html

Julien Grall

Xen-devel mailing list



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