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Subject: Re: [PATCH 00/10] GICv3 support for kexec/kdump on EFI systems
To:     Marc Zyngier <marc.zyngier@arm.com>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Cc:     Jeffrey Hugo <jhugo@codeaurora.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Jeremy Linton <jeremy.linton@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>
References: <20180921195954.21574-1-marc.zyngier@arm.com>
From:   Richard Ruigrok <rruigrok@codeaurora.org>
Message-ID: <44ac1fad-8df4-4738-0f25-8a7a2de8f6df@codeaurora.org>
Date:   Thu, 27 Sep 2018 15:10:50 -0600
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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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