From: Peng Hao Date: Tue, 8 Nov 2022 03:50:54 +0000 (+0800) Subject: KVM: x86: Keep the lock order consistent between SRCU and gpc spinlock X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4265df667bbdc71c640e43c905bd9aeeead92365;p=linux.git KVM: x86: Keep the lock order consistent between SRCU and gpc spinlock Acquire SRCU before taking the gpc spinlock in wait_pending_event() so as to be consistent with all other functions that acquire both locks. It's not illegal to acquire SRCU inside a spinlock, nor is there deadlock potential, but in general it's preferable to order locks from least restrictive to most restrictive, e.g. if wait_pending_event() needed to sleep for whatever reason, it could do so while holding SRCU, but would need to drop the spinlock. Signed-off-by: Peng Hao Reviewed-by: Sean Christopherson Link: https://lore.kernel.org/r/CAPm50a++Cb=QfnjMZ2EnCj-Sb9Y4UM-=uOEtHAcjnNLCAAf-dQ@mail.gmail.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 9187d024d0066..2f21fa5ee7de2 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -1165,8 +1165,8 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports, bool ret = true; int idx, i; - read_lock_irqsave(&gpc->lock, flags); idx = srcu_read_lock(&kvm->srcu); + read_lock_irqsave(&gpc->lock, flags); if (!kvm_gpc_check(kvm, gpc, gpc->gpa, PAGE_SIZE)) goto out_rcu; @@ -1187,8 +1187,8 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports, } out_rcu: - srcu_read_unlock(&kvm->srcu, idx); read_unlock_irqrestore(&gpc->lock, flags); + srcu_read_unlock(&kvm->srcu, idx); return ret; }