Hi Richard,

On 27/09/18 22:10, Richard Ruigrok wrote:

Hi Marc

On 9/21/2018 1:59 PM, Marc Zyngier wrote:

quoted

The GICv3 architecture has the remarkable feature that once LPI tables
have been assigned to redistributors and that LPI delivery is enabled,
there is no guarantee that LPIs can be turned off (and most
implementations do not allow it), nor can it be reprogrammed to use
other tables.

This is a bit of a problem for kexec, where the secondary kernel
completely looses track of the previous allocations. If the secondary
kernel doesn't allocate the tables exactly the same way, no LPIs will
be delivered by the GIC (which continues to use the old tables), and
memory previously allocated for the pending tables will be slowly
corrupted, one bit at a time.

The workaround for this is based on a series[1] by Ard Biesheuvel,
which adds the required infrastructure for memory reservations to be
passed from one kernel to another using an EFI table.

This infrastructure is then used to register the allocation of GIC
tables with EFI, and allow the GIC driver to safely reuse the existing
programming if it detects that the tables have been correctly
registered. On non-EFI systems, there is not much we can do.

This has been tested on a TX2 system both as a host and a guest. I'd
welcome additional testing of different HW. For convenience, I've
stashed a branch containing the whole thing at [2].

I tested [2] from the 4.19-rc4 set which included this series and [1].
Tested kexec on Centriq system with ITS support (46 core).? On-board was a MLX CX5 NIC, verified MSIs are active in /proc/interrupts.
Prior to this we used a workaround from Shanker to reuse the same tables in the kexec'ed kernel.

Yes, I remember seeing this workaround. Hopefully we're in a better 
place now that we can guarantee that the tables are not reused.

Let me know if further testing is needed, and thanks for adding this support.

Good to know, thanks for having tested it. I've now put this code into 
-next for some more soaking. Hopefully nothing horrible will happen ;-)

	M.
-- 
Jazz is not dead. It just smells funny...