Hi Marc On 9/21/2018 1:59 PM, Marc Zyngier wrote: > 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. Let me know if further testing is needed, and thanks for adding this support. > [1] https://marc.info/?l=linux-efi&m=153754757208163&w=2 > [2] > https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/gicv3-kdump > > Marc Zyngier (10): > irqchip/gic-v3-its: Change initialization ordering for LPIs > irqchip/gic-v3-its: Consolidate LPI_PENDBASE_SZ usage > irqchip/gic-v3-its: Split property table clearing from allocation > irqchip/gic-v3-its: Move pending table allocation to init time > irqchip/gic-v3-its: Keep track of property table's PA and VA > irqchip/gic-v3-its: Allow use of pre-programmed LPI tables > irqchip/gic-v3-its: Use pre-programmed redistributor tables with kdump > kernels > irqchip/gic-v3-its: Check that all RDs have the same property table > irqchip/gic-v3-its: Register LPI tables with EFI config table > irqchip/gic-v3-its: Allow use of LPI tables in reserved memory > > drivers/irqchip/irq-gic-v3-its.c | 249 ++++++++++++++++++++++------- > drivers/irqchip/irq-gic-v3.c | 20 ++- > include/linux/irqchip/arm-gic-v3.h | 4 +- > 3 files changed, 208 insertions(+), 65 deletions(-) >
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