releases/4.14.97/s390-early-improve-machine-detection.patch

   1 From 03aa047ef2db4985e444af6ee1c1dd084ad9fb4c Mon Sep 17 00:00:00 2001
   2 From: Christian Borntraeger <borntraeger@de.ibm.com>
   3 Date: Fri, 9 Nov 2018 09:21:47 +0100
   4 Subject: s390/early: improve machine detection
   5
   6 From: Christian Borntraeger <borntraeger@de.ibm.com>
   7
   8 commit 03aa047ef2db4985e444af6ee1c1dd084ad9fb4c upstream.
   9
  10 Right now the early machine detection code check stsi 3.2.2 for "KVM"
  11 and set MACHINE_IS_VM if this is different. As the console detection
  12 uses diagnose 8 if MACHINE_IS_VM returns true this will crash Linux
  13 early for any non z/VM system that sets a different value than KVM.
  14 So instead of assuming z/VM, do not set any of MACHINE_IS_LPAR,
  15 MACHINE_IS_VM, or MACHINE_IS_KVM.
  16
  17 CC: stable@vger.kernel.org
  18 Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
  19 Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
  20 Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
  21 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  22
  23 ---
  24  arch/s390/kernel/early.c |    4 ++--
  25  arch/s390/kernel/setup.c |    2 ++
  26  2 files changed, 4 insertions(+), 2 deletions(-)
  27
  28 --- a/arch/s390/kernel/early.c
  29 +++ b/arch/s390/kernel/early.c
  30 @@ -226,10 +226,10 @@ static noinline __init void detect_machi
  31         if (stsi(vmms, 3, 2, 2) || !vmms->count)
  32                 return;
  33
  34 -       /* Running under KVM? If not we assume z/VM */
  35 +       /* Detect known hypervisors */
  36         if (!memcmp(vmms->vm[0].cpi, "\xd2\xe5\xd4", 3))
  37                 S390_lowcore.machine_flags |= MACHINE_FLAG_KVM;
  38 -       else
  39 +       else if (!memcmp(vmms->vm[0].cpi, "\xa9\x61\xe5\xd4", 4))
  40                 S390_lowcore.machine_flags |= MACHINE_FLAG_VM;
  41  }
  42
  43 --- a/arch/s390/kernel/setup.c
  44 +++ b/arch/s390/kernel/setup.c
  45 @@ -884,6 +884,8 @@ void __init setup_arch(char **cmdline_p)
  46                 pr_info("Linux is running under KVM in 64-bit mode\n");
  47         else if (MACHINE_IS_LPAR)
  48                 pr_info("Linux is running natively in 64-bit mode\n");
  49 +       else
  50 +               pr_info("Linux is running as a guest in 64-bit mode\n");
  51
  52         /* Have one command line that is parsed and saved in /proc/cmdline */
  53         /* boot_command_line has been already set up in early.c */