I am interested in evaluating if using this is feasible for our
Android devices. There is quite a usecase for lockup detection that it
seems worthwhile if it works well. Atleast I feel this can be used a
debug option considering the performance downgrade.
Do you have more details of if any GICv3 based system will work, or is
there a way an SoC can be misconfigured so that this series will not
work? I think Marc told me that's possible, but I wasn't sure. I will
be quite happy if it works on SoC as long as they have the requisite
Some more questions below:
On Wed, Jan 17, 2018 at 3:54 AM, Julien Thierry <julien.thierry@xxxxxxx> wrote:
This series is a continuation of the work started by Daniel . The goal
is to use GICv3 interrupt priorities to simulate an NMI.
To achieve this, set two priorities, one for standard interrupts and
another, higher priority, for NMIs. Whenever we want to disable interrupts,
we mask the standard priority instead so NMIs can still be raised. Some
corner cases though still require to actually mask all interrupts
effectively disabling the NMI.
Of course, using priority masking instead of PSR.I comes at some cost. On
hackbench, the drop of performance seems to be >1% on average for this
version. I can only attribute that to recent changes in the kernel as
Do you have more specific performance data on the performance overhead
with this series?
hackbench seems slightly slower compared to my other benchmarks while the
runs with the use of GICv3 priorities have stayed in the same time frames.
KVM Guests do not seem to be affected preformance-wise by the host using
PMR to mask interrupts or not.
Currently, only PPIs and SPIs can be set as NMIs. IPIs being currently
hardcoded IRQ numbers, there isn't a generic interface to set SGIs as NMI
for now. I don't think there is any reason LPIs should be allowed to be set
as NMI as they do not have an active state.
When an NMI is active on a CPU, no other NMI can be triggered on the CPU.
Requirements to use this:
- Have GICv3
- SCR_EL3.FIQ is set to 1 when linux runs
Ah I see it mentioned here. Again, can you clarify if this is
something that can be misconfigured? Is it something that the
Sorry if these questions sound premature, I haven't yet taken a closerCheers,
look at the series.