Hi Marc > -----Original Message----- > From: linux-arm-kernel > [mailto:linux-arm-kernel-boun...@lists.infradead.org] On Behalf Of Marc > Zyngier > Sent: Saturday, September 22, 2018 5:00 AM > To: linux-kernel@vger.kernel.org; linux-arm-ker...@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 <zhang....@jp.fujitsu.com> Thanks a lot. Best Regards, Lei,Zhang FUJITSU LIMITED.
