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s390/nmi: handle vector validity failures for KVM guests

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commit f094a39c6b 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: c929500d7a ("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>
This commit is contained in:
Christian Borntraeger 2022-01-17 18:40:32 +01:00 committed by Greg Kroah-Hartman
parent c058e1ae9d
commit cfd2a7f8de
1 changed files with 8 additions and 1 deletions
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9
arch/s390/kernel/nmi.c
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@ -273,7 +273,14 @@ static int notrace s390_validate_registers(union mci mci, int umode)
/* 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