From: Christian Borntraeger borntraeger@linux.ibm.com
commit f094a39c6ba168f2df1edfd1731cca377af5f442 upstream.
The machine check validity bit tells about the context. If a KVM guest was running the bit tells about the guest validity and the host state is not affected. As a guest can disable the guest validity this might result in unwanted host errors on machine checks.
Cc: stable@vger.kernel.org Fixes: c929500d7a5a ("s390/nmi: s390: New low level handling for machine check happening in guest") Signed-off-by: Christian Borntraeger borntraeger@linux.ibm.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/kernel/nmi.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/arch/s390/kernel/nmi.c +++ b/arch/s390/kernel/nmi.c @@ -273,7 +273,14 @@ static int notrace s390_validate_registe /* Validate vector registers */ union ctlreg0 cr0;
- if (!mci.vr) { + /* + * The vector validity must only be checked if not running a + * KVM guest. For KVM guests the machine check is forwarded by + * KVM and it is the responsibility of the guest to take + * appropriate actions. The host vector or FPU values have been + * saved by KVM and will be restored by KVM. + */ + if (!mci.vr && !test_cpu_flag(CIF_MCCK_GUEST)) { /* * Vector registers can't be restored. If the kernel * currently uses vector registers the system is