[PATCH 4.4 11/65] s390/early: improve machine detection

Greg Kroah-Hartman
2019-02-04T10:39:44Z

From: Christian Borntraeger <borntraeger@de.ibm.com>

commit 03aa047ef2db4985e444af6ee1c1dd084ad9fb4c upstream.

Right now the early machine detection code check stsi 3.2.2 for "KVM"
and set MACHINE_IS_VM if this is different. As the console detection
uses diagnose 8 if MACHINE_IS_VM returns true this will crash Linux
early for any non z/VM system that sets a different value than KVM.
So instead of assuming z/VM, do not set any of MACHINE_IS_LPAR,
MACHINE_IS_VM, or MACHINE_IS_KVM.

CC: stable@vger.kernel.org
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/kernel/early.c | 4 ++--
arch/s390/kernel/setup.c | 2 ++
2 files changed, 4 insertions(+), 2 deletions(-)

--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -224,10 +224,10 @@ static noinline __init void detect_machi
if (stsi(vmms, 3, 2, 2) || !vmms->count)
return;

- /* Running under KVM? If not we assume z/VM */
+ /* Detect known hypervisors */
if (!memcmp(vmms->vm[0].cpi, "\xd2\xe5\xd4", 3))
S390_lowcore.machine_flags |= MACHINE_FLAG_KVM;
- else
+ else if (!memcmp(vmms->vm[0].cpi, "\xa9\x61\xe5\xd4", 4))
S390_lowcore.machine_flags |= MACHINE_FLAG_VM;
}

--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -833,6 +833,8 @@ void __init setup_arch(char **cmdline_p)
pr_info("Linux is running under KVM in 64-bit mode\n");
else if (MACHINE_IS_LPAR)
pr_info("Linux is running natively in 64-bit mode\n");
+ else
+ pr_info("Linux is running as a guest in 64-bit mode\n");

/* Have one command line that is parsed and saved in /proc/cmdline */
/* boot_command_line has been already set up in early.c */