From: David Stevens <stevensd@xxxxxxxxxxxx> Simplify locking in the case where the guest's runstate_info is split across two pages by sharing a single lock for the two gpcs. Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx> --- I tested this patch with xen_shinfo_test as suggested, and it still passes. I agree that it makes sense to do this as a seperate patch. For the bot reported issue, looks like I forgot to build with lockdep enabled. I'll fix the issue with that patch in the next revision of the series, so that there aren't any commits which don't build. arch/x86/kvm/xen.c | 25 ++++--------------------- 1 file changed, 4 insertions(+), 21 deletions(-) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index fa8ab23271d3..9251f88a4e0d 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -310,24 +310,10 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic) update_bit = ((void *)(&rs_times[1])) - 1; } else { /* - * The guest's runstate_info is split across two pages and we - * need to hold and validate both GPCs simultaneously. We can - * declare a lock ordering GPC1 > GPC2 because nothing else - * takes them more than one at a time. Set a subclass on the - * gpc1 lock to make lockdep shut up about it. + * The GPCs for both pages which comprise the guest's + * runstate_info share a lock, and it's already locked. */ - lock_set_subclass(gpc1->lock.dep_map, 1, _THIS_IP_); - if (atomic) { - if (!read_trylock(gpc2->lock)) { - read_unlock_irqrestore(gpc1->lock, flags); - return; - } - } else { - read_lock(gpc2->lock); - } - if (!kvm_gpc_check(gpc2, user_len2)) { - read_unlock(gpc2->lock); read_unlock_irqrestore(gpc1->lock, flags); /* When invoked from kvm_sched_out() we cannot sleep */ @@ -427,9 +413,6 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic) smp_wmb(); } - if (user_len2) - read_unlock(gpc2->lock); - read_unlock_irqrestore(gpc1->lock, flags); mark_page_dirty_in_slot(v->kvm, gpc1->memslot, gpc1->gpa >> PAGE_SHIFT); @@ -2056,8 +2039,8 @@ void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu) kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm, NULL, KVM_HOST_USES_PFN); - kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm, NULL, - KVM_HOST_USES_PFN); + kvm_gpc_init_with_lock(&vcpu->arch.xen.runstate2_cache, vcpu->kvm, NULL, + KVM_HOST_USES_PFN, vcpu->arch.xen.runstate_cache.lock); kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache, vcpu->kvm, NULL, KVM_HOST_USES_PFN); kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache, vcpu->kvm, NULL, -- 2.39.1.456.gfc5497dd1b-goog