Re: [PATCH 00/10] GICv3 support for kexec/kdump on EFI systems

[Marc Zyngier]

Hi Richard,

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

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...