• Vitaly Kuznetsov's avatar
    arm/xen: fix SMP guests boot · de75abbe
    Vitaly Kuznetsov authored
    Commit 88e957d6 ("xen: introduce xen_vcpu_id mapping") broke SMP
    ARM guests on Xen. When FIFO-based event channels are in use (this is
    the default), evtchn_fifo_alloc_control_block() is called on
    CPU_UP_PREPARE event and this happens before we set up xen_vcpu_id
    mapping in xen_starting_cpu. Temporary fix the issue by setting direct
    Linux CPU id <-> Xen vCPU id mapping for all possible CPUs at boot. We
    don't currently support kexec/kdump on Xen/ARM so these ids always
    match.
    
    In future, we have several ways to solve the issue, e.g.:
    
    - Eliminate all hypercalls from CPU_UP_PREPARE, do them from the
      starting CPU. This can probably be done for both x86 and ARM and, if
      done, will allow us to get Xen's idea of vCPU id from CPUID/MPIDR on
      the starting CPU directly, no messing with ACPI/device tree
      required.
    
    - Save vCPU id information from ACPI/device tree on ARM and use it to
      initialize xen_vcpu_id mapping. This is the same trick we currently
      do on x86.
    Reported-by: default avatarJulien Grall <julien.grall@arm.com>
    Tested-by: default avatarWei Chen <Wei.Chen@arm.com>
    Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
    Acked-by: default avatarStefano Stabellini <sstabellini@kernel.org>
    Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
    de75abbe
enlighten.c 12.2 KB