Re: Ping: [PATCH v15 00/13] support "task_isolation" mode

On 2016-09-07 05:11 PM, Francis Giraldeau wrote:

The syscall test fails on x86:
    $ sudo ./isolation
    [...]
    test_syscall: FAIL (0x100)
    test_syscall (SIGUSR1): FAIL (0x100)

I wanted to debug this problem with gdb and a KVM virtual machine. However, the TSC clock source is detected as non reliable, even with the boot parameter tsc=reliable, and therefore prctl(PR_SET_TASK_ISOLATION, PR_TASK_ISOLATION_ENABLE) always returns EAGAIN. Is there a trick to run task isolation in a VM (at least for debugging purposes)?

OK, got it. The guest kernel must be compiled with CONFIG_KVM_GUEST, and then with virsh edit, set the clock configuration of the VM (under <domain>):

 <clock offset='utc'>
    <timer name='kvmclock'/>
  </clock>

Of course, the jitter is horrible, but at least it is possible to debug with GDB.

Cheers,

Francis