[OS-BUILD PATCH] Redhat: enable Kfence on production servers

[Nico Pache (via Email Bridge)]

From: Nico Pache <npache(a)redhat.com&gt;

Redhat: enable Kfence on production servers

Kfence allows for a low overhead memory error detection system that can
be deployed in production. By enabling this feature we allow for better
and quicker bug reporting/fixing.

the Kscale team has done some performance testing and have concluded
there is no noticable performance impact.

Enable for ELN and remove the Fedora specific config definition.
We may want to consider enabling CONFIG_KFENCE_DEFERRABLE on fedora...
This config allows the CPU wakup to be deferred, which is more ideal for
power-constrianted systems which is more likely to be the case on Fedora.

Signed-off-by: Nico Pache npache(a)redhat.com

diff --git a/redhat/configs/common/debug/CONFIG_KFENCE
b/redhat/configs/common/debug/CONFIG_KFENCE
new file mode 100644
index blahblah..blahblah 100644
--- /dev/null
+++ b/redhat/configs/common/debug/CONFIG_KFENCE
@@ -0,0 +1 @@
+# CONFIG_KFENCE is not set
diff --git a/redhat/configs/common/generic/CONFIG_KFENCE
b/redhat/configs/common/generic/CONFIG_KFENCE
index blahblah..blahblah 100644
--- a/redhat/configs/common/generic/CONFIG_KFENCE
+++ b/redhat/configs/common/generic/CONFIG_KFENCE
@@ -1 +1 @@
-# CONFIG_KFENCE is not set
+CONFIG_KFENCE=y
diff --git a/redhat/configs/common/generic/CONFIG_KFENCE_DEFERRABLE
b/redhat/configs/common/generic/CONFIG_KFENCE_DEFERRABLE
new file mode 100644
index blahblah..blahblah 100644
--- /dev/null
+++ b/redhat/configs/common/generic/CONFIG_KFENCE_DEFERRABLE
@@ -0,0 +1 @@
+# CONFIG_KFENCE_DEFERRABLE is not set
diff --git a/redhat/configs/fedora/generic/CONFIG_KFENCE_NUM_OBJECTS
b/redhat/configs/common/generic/CONFIG_KFENCE_NUM_OBJECTS
rename from redhat/configs/fedora/generic/CONFIG_KFENCE_NUM_OBJECTS
rename to redhat/configs/common/generic/CONFIG_KFENCE_NUM_OBJECTS
index blahblah..blahblah 100644
--- a/redhat/configs/fedora/generic/CONFIG_KFENCE_NUM_OBJECTS
+++ b/redhat/configs/common/generic/CONFIG_KFENCE_NUM_OBJECTS
diff --git a/redhat/configs/common/generic/CONFIG_KFENCE_SAMPLE_INTERVAL
b/redhat/configs/common/generic/CONFIG_KFENCE_SAMPLE_INTERVAL
new file mode 100644
index blahblah..blahblah 100644
--- /dev/null
+++ b/redhat/configs/common/generic/CONFIG_KFENCE_SAMPLE_INTERVAL
@@ -0,0 +1 @@
+CONFIG_KFENCE_SAMPLE_INTERVAL=100
diff --git a/redhat/configs/common/generic/CONFIG_KFENCE_STATIC_KEYS
b/redhat/configs/common/generic/CONFIG_KFENCE_STATIC_KEYS
new file mode 100644
index blahblah..blahblah 100644
--- /dev/null
+++ b/redhat/configs/common/generic/CONFIG_KFENCE_STATIC_KEYS
@@ -0,0 +1 @@
+CONFIG_KFENCE_STATIC_KEYS=y
diff --git a/redhat/configs/fedora/generic/CONFIG_KFENCE
b/redhat/configs/fedora/generic/CONFIG_KFENCE
deleted file mode 100644
index blahblah..blahblah 0
--- a/redhat/configs/fedora/generic/CONFIG_KFENCE
+++ /dev/null
@@ -1 +0,0 @@
-CONFIG_KFENCE=y
diff --git a/redhat/configs/fedora/generic/CONFIG_KFENCE_SAMPLE_INTERVAL
b/redhat/configs/fedora/generic/CONFIG_KFENCE_SAMPLE_INTERVAL
deleted file mode 100644
index blahblah..blahblah 0
--- a/redhat/configs/fedora/generic/CONFIG_KFENCE_SAMPLE_INTERVAL
+++ /dev/null
@@ -1 +0,0 @@
-CONFIG_KFENCE_SAMPLE_INTERVAL=0

--
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748

[Nico Pache (via Email Bridge)]

From: Nico Pache on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9085...

There will most likely be `CKI::Failed kernel-results` here. Its a known issue
with the parser. The test actually passes. I will work on fixing that now.
*probably should have done that first*

[Justin M. Forbes (via Email Bridge)]

From: Justin M. Forbes on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9086...

Curious on CONFIG_KFENCE_STATIC_KEYS, was there benchmarking done both enabled
and disabled? Just asking because the help text seemed to indicate it was
"only recommended when using very large sample intervals, or performance has
carefully been evaluated with this option."  I would not consider 100 to be a
"very large sample interval" so is it worth the trade off?

[Nico Pache (via Email Bridge)]

From: Nico Pache on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9086...

No, no other config was tested. The test suite that was run was pretty
thorough and noted no change in performance. Ill send you the details in a
private note.

As for why I enabled it, per the help text: `static keys is normally
recommended`

[Justin M. Forbes (via Email Bridge)]

From: Justin M. Forbes on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9086...

Actually commit 4f612ed3f748962cbef1316ff3d323e2b9055b6e changed it to depend
on CONFIG_EXPERT, which is not set, so there is no need for an entry on either
CONFIG_KFENCE_STATIC_KEYS and it will be set to off.

[Nico Pache (via Email Bridge)]

From: Nico Pache on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9086...

Interesting... Good catch. Let me circle back with the Kscale team, and see if
they can test with this changed to =N. Based on that commit it seems the
performance issues arise in systems with a very large amount of CPUs, which im
not sure were tested.

[Bruno Goncalves (via Email Bridge)]

From: Bruno Goncalves on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9166...

@npache I used to bot to test this MR, but it failed to build for x86_64:
https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/...
trusted-contributors/-/jobs/2349465582 the failure doesn't seem related to the
MR though...

[Justin Forbes]

On Tue, Apr 19, 2022 at 7:48 AM Bruno Goncalves (via Email Bridge)
<cki-gitlab(a)redhat.com&gt; wrote:
>  From: Bruno Goncalves on gitlab.com
>  https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9166...
>
>  @npache I used to bot to test this MR, but it failed to build for x86_64:
>  https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/...
>  trusted-contributors/-/jobs/2349465582 the failure doesn't seem related to the
>  MR though... 
It is indeed unrelated. You are attempting to build with a broken GCC.
Ths bug was fixed with gcc-12.0.1-0.16 builds

Justin

[Nico Pache (via Email Bridge)]

From: Nico Pache on gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1748#note_9169...

Kscale team confirms no performance degradation with STATIC_KEYS=n. It was
tested on larger and newer systems as well.