chore: drop support for Skylake instances

We're dropping official support for our oldest supported instance type.
There is no functional change, meaning Firecracker will continue to work
on that instance type, but we will drop all automated testing on it.

Signed-off-by: Riccardo Mancini <[email protected]>

Author: Manciukic

.buildkite/common.py

@@ -16,9 +16,8 @@
 
 # fmt: off
 DEFAULT_INSTANCES = [
-    "c5n.metal",      # Intel Skylake
     "m5n.metal",      # Intel Cascade Lake
-    "m6i.metal",      # Intel Icelake
+    "m6i.metal",      # Intel Ice Lake
     "m7i.metal-24xl", # Intel Sapphire Rapids
     "m7i.metal-48xl", # Intel Sapphire Rapids
     "m6a.metal",      # AMD Milan

.buildkite/pipeline_cpu_template.py

@@ -27,7 +27,6 @@ class BkStep(str, Enum):
         ],
         BkStep.LABEL: "📖 rdmsr",
         "instances": [
-            "c5n.metal",
             "m5n.metal",
             "m6i.metal",
             "m7i.metal-24xl",
@@ -63,12 +62,10 @@ class BkStep(str, Enum):
             BkStep.TIMEOUT: 30,
         },
         "cross_instances": {
-            "m5n.metal": ["c5n.metal", "m6i.metal"],
-            "c5n.metal": ["m5n.metal", "m6i.metal"],
-            "m6i.metal": ["m5n.metal", "c5n.metal"],
+            "m5n.metal": ["m6i.metal"],
+            "m6i.metal": ["m5n.metal"],
         },
         "instances": [
-            "c5n.metal",
             "m5n.metal",
             "m6i.metal",
             "m7i.metal-24xl",

.buildkite/pipeline_cross.py

@@ -19,7 +19,6 @@
     per_instance.pop("instances")
     per_instance.pop("platforms")
     instances_x86_64 = [
-        "c5n.metal",
         "m5n.metal",
         "m6i.metal",
         "m7i.metal-24xl",
@@ -49,9 +48,8 @@
     # allow-list of what instances can be restores on what other instances (in
     # addition to itself)
     supported = {
-        "c5n.metal": ["m5n.metal", "m6i.metal"],
-        "m5n.metal": ["c5n.metal", "m6i.metal"],
-        "m6i.metal": ["c5n.metal", "m5n.metal"],
+        "m5n.metal": ["m6i.metal"],
+        "m6i.metal": ["m5n.metal"],
     }
 
     # https://github.com/firecracker-microvm/firecracker/blob/main/docs/kernel-policy.md#experimental-snapshot-compatibility-across-kernel-versions
@@ -82,7 +80,6 @@
             continue
 
         pytest_keyword_for_instance = {
-            "c5n.metal": "-k 'not None'",
             "m5n.metal": "-k 'not None'",
             "m6i.metal": "-k 'not None'",
             "m6a.metal": "",

CHANGELOG.md

@@ -84,6 +84,11 @@ and this project adheres to
 
 ### Removed
 
+- [#5411](https://github.com/firecracker-microvm/firecracker/pull/5411): Removed
+  official support for Intel Skylake instances. Firecracker will continue to
+  work on those instances, but we will no longer perform automated testing on
+  them.
+
 ### Fixed
 
 - [#5222](https://github.com/firecracker-microvm/firecracker/pull/5222): Fixed

README.md

@@ -130,19 +130,18 @@ The **API endpoint** can be used to:
 
 We test all combinations of:
 
-| Instance       | Host OS & Kernel | Guest Rootfs | Guest Kernel |
-| :------------- | :--------------- | :----------- | :----------- |
-| c5n.metal      | al2 linux_5.10   | ubuntu 24.04 | linux_5.10   |
-| m5n.metal      | al2023 linux_6.1 |              | linux_6.1    |
-| m6i.metal      |                  |              |              |
-| m7i.metal-24xl |                  |              |              |
-| m7i.metal-48xl |                  |              |              |
-| m6a.metal      |                  |              |              |
-| m7a.metal-48xl |                  |              |              |
-| m6g.metal      |                  |              |              |
-| m7g.metal      |                  |              |              |
-| m8g.metal-24xl |                  |              |              |
-| m8g.metal-48xl |                  |              |              |
+| Instance                               | Host OS & Kernel | Guest Rootfs | Guest Kernel |
+| :------------------------------------- | :--------------- | :----------- | :----------- |
+| m5n.metal (Intel Cascade Lake)         | al2 linux_5.10   | ubuntu 24.04 | linux_5.10   |
+| m6i.metal (Intel Ice Lake)             | al2023 linux_6.1 |              | linux_6.1    |
+| m7i.metal-24xl (Intel Sapphire Rapids) |                  |              |              |
+| m7i.metal-48xl (Intel Sapphire Rapids) |                  |              |              |
+| m6a.metal (AMD Milan)                  |                  |              |              |
+| m7a.metal-48xl (AMD Genoa)             |                  |              |              |
+| m6g.metal (Graviton 2)                 |                  |              |              |
+| m7g.metal (Graviton 3)                 |                  |              |              |
+| m8g.metal-24xl (Graviton 4)            |                  |              |              |
+| m8g.metal-48xl (Graviton 4)            |                  |              |              |
 
 ## Known issues and Limitations
 

docs/snapshotting/snapshot-support.md

@@ -625,10 +625,11 @@ the compatibility table reported below:
 
 | .metal instance type | taken on host kernel | restored on host kernel |
 | -------------------- | -------------------- | ----------------------- |
-| {c5n,m5n,m6i,m6a}    | 5.10                 | 6.1                     |
+| {m5n,m6i,m6a}        | 5.10                 | 6.1                     |
 
-For example, a snapshot taken on a m6i.metal host running a 5.10 host kernel can
-be restored on a different m6i.metal host running a 6.1 host kernel (but not
-vice versa), but could not be restored on a c5n.metal host.
+For example, a snapshot taken on a m6i.metal host (Intel Ice Lake) running a
+5.10 host kernel can be restored on a different m6i.metal host running a 6.1
+host kernel (but not vice versa), but could not be restored on a m5n.metal host
+(Intel Cascade Lake).
 
 [man mincore]: https://man7.org/linux/man-pages/man2/mincore.2.html