| Message ID | 20230705111937.33472-2-imbrenda@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: s390: pv: fix two small bugs | expand |
Quoting Claudio Imbrenda (2023-07-05 13:19:36) > 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") > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c index 3ce5f4351156..899f3b8ac011 100644 --- a/arch/s390/kvm/pv.c +++ b/arch/s390/kvm/pv.c @@ -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") Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> --- arch/s390/kvm/pv.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)