s390/early: improve machine detection

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>

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 5b28b43..e7e6608 100644 (file)
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -64,10 +64,10 @@ static noinline __init void detect_machine_type(void)
        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;
 }
 

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index c637c12..a0097f8 100644 (file)
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -882,6 +882,8 @@ 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 */