On 25/05/18 11:40, Julien Thierry wrote:

On 25/05/18 11:16, Daniel Thompson wrote:

quoted

On Fri, May 25, 2018 at 10:49:06AM +0100, Julien Thierry wrote:

quoted

This series is a continuation of the work started by Daniel [1]. 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.

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.

After the big refactoring I get performances similar to the ones I had
in v3[2], reposting old results here:

- "hackbench 200 process 1000" (average over 20 runs)
+-----------+----------+------------+------------------+
|?????????? | native?? | PMR guest? | v4.17-rc6 guest? |
+-----------+----------+------------+------------------+
| PMR host? | 40.0336s |?? 39.3039s |???????? 39.2044s |
| v4.17-rc6 | 40.4040s |?? 39.6011s |???????? 39.1147s |
+-----------+----------+------------+------------------+

- Kernel build from defconfig:
PMR host:? 13m45.743s
v4.17-rc6: 13m40.400s

I'll try to post more detailed benchmarks later if I find notable
differences with the previous version.

Do you have a public git tree anywhere... I *can* apply 26 patches from
e-mail but I'd rather pull them!

Yes that makes sense, I'll try to get one set up.

I'll let you know once I have done so.

My public git is up. You can pull the patches from:

git://linux-arm.org/linux-jt.git v4.17-pseudo-nmi

Cheers,

-- 
Julien Thierry