@@ -411,8 +411,12 @@ int kvm_s390_pv_deinit_cleanup_all(struct kvm *kvm, u16 *rc, u16 *rrc)
u16 _rc, _rrc;
int cc = 0;
- /* Make sure the counter does not reach 0 before calling s390_uv_destroy_range */
- atomic_inc(&kvm->mm->context.protected_count);
+ /*
+ * Nothing to do if the counter was already 0. Otherwise make sure
+ * the counter does not reach 0 before calling s390_uv_destroy_range.
+ */
+ if (!atomic_inc_not_zero(&kvm->mm->context.protected_count))
+ return 0;
*rc = 1;
/* If the current VM is protected, destroy it */
Simplify the shutdown of non-protected VMs. There is no need to do complex manipulations of the counter if it was zero. This also fixes a very rare race which caused pages to be torn down from the address space with a non-zero counter even on older machines that don't support the UVC instruction, causing a crash. Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com> Fixes: fb491d5500a7 ("KVM: s390: pv: asynchronous destroy for reboot") Reviewed-by: Nico Boehr <nrb@linux.ibm.com> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Message-ID: <20230705111937.33472-2-imbrenda@linux.ibm.com> --- arch/s390/kvm/pv.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)