| Message ID | 20240217114017.11551-6-dwmw2@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/xen updates | expand |
On 17/02/2024 11:27, David Woodhouse wrote: > From: David Woodhouse <dwmw@amazon.co.uk> > > The fast-path timer delivery introduced a recursive locking deadlock > when userspace configures a timer which has already expired and is > delivered immediately. The call to kvm_xen_inject_timer_irqs() can > call to kvm_xen_set_evtchn() which may take kvm->arch.xen.xen_lock, > which is already held in kvm_xen_vcpu_get_attr(). > > ============================================ > WARNING: possible recursive locking detected > 6.8.0-smp--5e10b4d51d77-drs #232 Tainted: G O > -------------------------------------------- > xen_shinfo_test/250013 is trying to acquire lock: > ffff938c9930cc30 (&kvm->arch.xen.xen_lock){+.+.}-{3:3}, at: kvm_xen_set_evtchn+0x74/0x170 [kvm] > > but task is already holding lock: > ffff938c9930cc30 (&kvm->arch.xen.xen_lock){+.+.}-{3:3}, at: kvm_xen_vcpu_get_attr+0x38/0x250 [kvm] > > Now that the gfn_to_pfn_cache has its own self-sufficient locking, its > callers no longer need to ensure serialization, so just stop taking > kvm->arch.xen.xen_lock from kvm_xen_set_evtchn(). > > Fixes: 77c9b9dea4fb ("KVM: x86/xen: Use fast path for Xen timer delivery") > Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> > --- > arch/x86/kvm/xen.c | 4 ---- > 1 file changed, 4 deletions(-) > Reviewed-by: Paul Durrant <paul@xen.org>
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index e6c7353e5315..706af2935277 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -1903,8 +1903,6 @@ static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm) mm_borrowed = true; } - mutex_lock(&kvm->arch.xen.xen_lock); - /* * It is theoretically possible for the page to be unmapped * and the MMU notifier to invalidate the shared_info before @@ -1932,8 +1930,6 @@ static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm) srcu_read_unlock(&kvm->srcu, idx); } while(!rc); - mutex_unlock(&kvm->arch.xen.xen_lock); - if (mm_borrowed) kthread_unuse_mm(kvm->mm);