T7072: VPP CPU skip-cores should be verified

2 files changed, 28 insertions, 3 deletions

diff --git a/smoketest/scripts/cli/test_vpp.py b/smoketest/scripts/cli/test_vpp.py
index f504d2d95..03ee68beb 100755
--- a/smoketest/scripts/cli/test_vpp.py
+++ b/smoketest/scripts/cli/test_vpp.py
@@ -986,8 +986,9 @@ class TestVPP(VyOSUnitTestSHIM.TestCase):
             self.assertIn(f'{option} {value}', config)
 
     def test_11_vpp_cpu_settings(self):
-        main_core = '0'
+        main_core = '2'
         workers = '2'
+        skip_cores = '1'
 
         self.cli_set(base_path + ['settings', 'cpu', 'workers', workers])
 
@@ -998,9 +999,19 @@ class TestVPP(VyOSUnitTestSHIM.TestCase):
 
         self.cli_set(base_path + ['settings', 'cpu', 'main-core', main_core])
 
+        self.cli_set(base_path + ['settings', 'cpu', 'skip-cores', '99'])
+
+        # "cpu skip-cores" cannot be more than number of available CPUs - 1
+        # expect raise ConfigError
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+
+        self.cli_set(base_path + ['settings', 'cpu', 'skip-cores', skip_cores])
+
         self.cli_commit()
 
         config_entries = (
+            f'skip-cores {skip_cores}',
             f'main-core {main_core}',
             f'workers {workers}',
             'dev 0000:00:00.0',
diff --git a/src/conf_mode/vpp.py b/src/conf_mode/vpp.py
index 421556d07..bbdffa524 100755
--- a/src/conf_mode/vpp.py
+++ b/src/conf_mode/vpp.py
@@ -383,11 +383,23 @@ def verify(config):
             raise ConfigError('"cpu main-core" is required but not set!')
 
         cpus = int(get_core_count())
+        skip_cores = 0
+
+        if 'skip_cores' in config['settings']['cpu']:
+            skip_cores = int(config['settings']['cpu']['skip_cores'])
+            # the number of skipped cores should not be more than all CPUs - 1 (for main core)
+            if skip_cores > cpus - 1:
+                raise ConfigError(
+                    f'The system does not have enough available CPUs to skip '
+                    f'(reduce "cpu skip-cores" to {cpus - 1} or less)'
+                )
+
         if 'workers' in config['settings']['cpu']:
             # number of worker threads must be not more than
-            # available CPUs in the system - 2 (1 for main thread and at least 1 for system processes)
+            # available CPUs in the system - 1 for main thread - number of skipped cores
+            # or - 1 (at least) for system processes
             workers = int(config['settings']['cpu']['workers'])
-            available_workers = cpus - 2
+            available_workers = cpus - 1 - (skip_cores or 1)
             if workers > available_workers:
                 raise ConfigError(
                     f'The system does not have enough CPUs for {workers} VPP workers '
@@ -395,6 +407,8 @@ def verify(config):
                 )
 
         cpus_available = list(map(lambda el: el['cpu'], get_available_cpus()))
+        # available CPUs are all CPUs without first N skipped cores that will not be used
+        cpus_available = cpus_available[skip_cores:]
 
         if 'main_core' in config['settings']['cpu']:
             main_core = int(config['settings']['cpu']['main_core'])