KVM: PPC: Book3S HV: Hold kvm->lock around call to kvmppc_update_lpcr

Commit 468808bd35c4 ("KVM: PPC: Book3S HV: Set process table for HPT
guests on POWER9", 2017-01-30) added a call to kvmppc_update_lpcr()
which doesn't hold the kvm->lock mutex around the call, as required.
This adds the lock/unlock pair, and for good measure, includes
the kvmppc_setup_partition_table() call in the locked region, since
it is altering global state of the VM.

This error appears not to have any fatal consequences for the host;
the consequences would be that the VCPUs could end up running with
different LPCR values, or an update to the LPCR value by userspace
using the one_reg interface could get overwritten, or the update
done by kvmhv_configure_mmu() could get overwritten.

Cc: stable@vger.kernel.org # v4.10+
Fixes: 468808bd35c4 ("KVM: PPC: Book3S HV: Set process table for HPT guests on POWER9")
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 18e974a34fce..a7177c284f9b 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4212,11 +4212,13 @@ static int kvmhv_configure_mmu(struct kvm *kvm, struct kvm_ppc_mmuv3_cfg *cfg)
         if ((cfg->process_table & PRTS_MASK) > 24)
                 return -EINVAL;
 
+        mutex_lock(&kvm->lock);
         kvm->arch.process_table = cfg->process_table;
         kvmppc_setup_partition_table(kvm);
 
         lpcr = (cfg->flags & KVM_PPC_MMUV3_GTSE) ? LPCR_GTSE : 0;
         kvmppc_update_lpcr(kvm, lpcr, LPCR_GTSE);
+        mutex_unlock(&kvm->lock);
 
         return 0;
 }