Hi,
On 09/21/2018 02:59 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].
When combined with Ard's patch set, this fixes kdump on a QC machine.
Tested-by: Jeremy Linton <jeremy.lin...@arm.com>
Thanks,
[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(-)
