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SubjectRe: [PATCH v9 7/7] arm64: kgdb: Roundup cpus using the debug IPI
On 2023-08-07 11:28, Mark Rutland wrote:
> On Thu, Jun 01, 2023 at 02:31:51PM -0700, Douglas Anderson wrote:
>> From: Sumit Garg <sumit.garg@linaro.org>
>>
>> Let's use the debug IPI for rounding up CPUs in kgdb. When the debug
>> IPI is backed by an NMI (or pseudo NMI) then this will let us debug
>> even hard locked CPUs. When the debug IPI isn't backed by an NMI then
>> this won't really have any huge benefit but it will still work.
>>
>> Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
>> Signed-off-by: Douglas Anderson <dianders@chromium.org>
>> ---
>>
>> Changes in v9:
>> - Remove fallback for when debug IPI isn't available.
>> - Renamed "NMI IPI" to "debug IPI" since it might not be backed by
>> NMI.
>>
>> arch/arm64/kernel/ipi_debug.c | 5 +++++
>> arch/arm64/kernel/kgdb.c | 14 ++++++++++++++
>> 2 files changed, 19 insertions(+)
>
> This looks fine to me, but I'd feel a bit happier if we had separate
> SGIs for
> the backtrace and the KGDB callback as they're logically unrelated.

Well, we're a bit stuck here.

We have exactly *one* spare SGI with GICv3, as we lose 8 of them
to the secure side. One possibility would be to mux some of the
lesser used IPIs onto two SGIs (one with standard priority, and
one with NMI priority).

M.
--
Jazz is not dead. It just smells funny...

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