Hi Marc

-----Original Message-----
From: linux-arm-kernel
[mailto:linux-arm-kernel-bounces at lists.infradead.org] On Behalf Of Marc
Zyngier
Sent: Saturday, September 22, 2018 5:00 AM
To: linux-kernel at vger.kernel.org; linux-arm-kernel at lists.infradead.org
Cc: Jeffrey Hugo; Thomas Gleixner; Jason Cooper; Jeremy Linton; Ard
Biesheuvel
Subject: [PATCH 00/10] GICv3 support for kexec/kdump on EFI systems

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].

We have done the test on our chip A64FX that When a write changes 
EnableLPI bit from 0 to 1, this bit becomes RES1. 
The result is that the kexec operation successfully works on our chip,
 and PCI based on LPI also works after kexec.

For detail:
We did "kexec -e" command, and the message, "Using preallocated 
redistributor tables", was shown.
After kexec, we can use our ssd normally.

Test environment
CPU: A64FX

Kernel version: v4.19 rc4 base
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/gicv3-kdump
8bc67da irqchip/gic-v3-its: Allow use of LPI tables in reserved memory

kexec version:kexec-tools-2.0.14-17.2.el7.aarch64

Tested-by: Lei Zhang <redacted>

Thanks a lot.

Best Regards,
Lei,Zhang
FUJITSU LIMITED.