[PATCH v9 1/6] KVM: s390: do not clobber registers during guest reset/store status

Janosch Frank
2020-01-30T12:34:51Z

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

The initial CPU reset clobbers the userspace fpc and the store status
ioctl clobbers the guest acrs + fpr. As these calls are only done via
ioctl (and not via vcpu_run), no CPU context is loaded, so we can (and
must) act directly on the sync regs, not on the thread context.

Cc: stable@kernel.org
Fixes: e1788bb995be ("KVM: s390: handle floating point registers in the run ioctl not in vcpu_put/load")
Fixes: 31d8b8d41a7e ("KVM: s390: handle access registers in the run ioctl not in vcpu_put/load")
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
arch/s390/kvm/kvm-s390.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c059b86aacd4..328dee666b24 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2824,8 +2824,7 @@ static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu)
vcpu->arch.sie_block->gcr[14] = CR14_UNUSED_32 |
CR14_UNUSED_33 |
CR14_EXTERNAL_DAMAGE_SUBMASK;
- /* make sure the new fpc will be lazily loaded */
- save_fpu_regs();
+ vcpu->run->s.regs.fpc = 0;
current->thread.fpu.fpc = 0;
vcpu->arch.sie_block->gbea = 1;
vcpu->arch.sie_block->pp = 0;
@@ -4343,7 +4342,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
switch (ioctl) {
case KVM_S390_STORE_STATUS:
idx = srcu_read_lock(&vcpu->kvm->srcu);
- r = kvm_s390_vcpu_store_status(vcpu, arg);
+ r = kvm_s390_store_status_unloaded(vcpu, arg);
srcu_read_unlock(&vcpu->kvm->srcu, idx);
break;
case KVM_S390_SET_INITIAL_PSW: {
--
2.20.1