Fix --apend_kernel_commandline in RHEL 9+ based OSes.

https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/9.3_release_notes/new-features#new-features-boot-loader

PiperOrigin-RevId: 829495608

Author: pmkc

perfkitbenchmarker/linux_virtual_machine.py

@@ -798,10 +798,9 @@ def _DisableCpus(self):
 
     if self.num_disable_cpus <= 0 or self.num_disable_cpus >= self.num_cpus:
       raise ValueError(
-          'num_disable_cpus must be between 1 and '
-          '(num_cpus - 1) inclusive.  '
-          'num_disable_cpus: %i, num_cpus: %i'
-          % (self.num_disable_cpus, self.num_cpus)
+          'num_disable_cpus must be between 1 and (num_cpus - 1) inclusive.  '
+          f'num_disable_cpus: {self.num_disable_cpus}, '
+          f'num_cpus: {self.num_cpus}'
       )
 
     # We can't disable cpu 0, starting from the last cpu in /proc/cpuinfo.
@@ -1690,6 +1689,8 @@ def _AfterReboot(self):
     self._kernel_release = None
     self._kernel_command_line = None
     self._lscpu_cache = None
+    # recalculated in RecordAdditionalMetadata
+    self.num_cpus = None
     self.RecordAdditionalMetadata()
     if self.install_packages:
       self._CreateInstallDir()
@@ -2774,8 +2775,14 @@ def AppendKernelCommandLine(self, command_line, reboot=True):
         r'echo GRUB_CMDLINE_LINUX_DEFAULT=\"\${GRUB_CMDLINE_LINUX_DEFAULT} %s\"'
         ' | sudo tee -a /etc/default/grub' % command_line
     )
-    self.RemoteCommand('sudo grub2-mkconfig -o /boot/grub2/grub.cfg')
-    self.RemoteCommand('sudo grub2-mkconfig -o /etc/grub2.cfg')
+    # RHEL 9.3+ requires a flag to update the kernel command line.
+    # It does not exist in older versions.
+    # https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/9.3_release_notes/new-features#new-features-boot-loader
+    update_grub = 'sudo grub2-mkconfig'
+    if self.TryRemoteCommand(f'{update_grub} --update-bls-cmdline'):
+      update_grub += ' --update-bls-cmdline'
+    self.RemoteCommand(f'{update_grub} -o /boot/grub2/grub.cfg')
+    self.RemoteCommand(f'{update_grub} -o /etc/grub2.cfg')
     if reboot:
       self.Reboot()