From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: [PATCHv1 2/2] passthrough: improve locking when iterating over interrupts bound to VMs Date: Fri, 23 Oct 2015 12:05:22 +0100 Message-ID: <1445598322-22154-3-git-send-email-david.vrabel@citrix.com> References: <1445598322-22154-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZpaA6-0003bW-BS for xen-devel@lists.xenproject.org; Fri, 23 Oct 2015 11:05:30 +0000 In-Reply-To: <1445598322-22154-1-git-send-email-david.vrabel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: xen-devel@lists.xenproject.org Cc: David Vrabel , Jan Beulich , Ian Campbell List-Id: xen-devel@lists.xenproject.org radix_tree_gang_lookup() only requires a RCU read lock, not the per-domain event_lock. Introduce a new RCU read lock and take the per-interrupt lock before calling the callback instead. This eliminates all contention on the event_lock when injecting interrupts from passthrough devices. Signed-off-by: David Vrabel --- xen/drivers/passthrough/io.c | 10 +++++++--- xen/include/xen/sched.h | 1 + 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/xen/drivers/passthrough/io.c b/xen/drivers/passthrough/io.c index 7c86c20..9b51ef0 100644 --- a/xen/drivers/passthrough/io.c +++ b/xen/drivers/passthrough/io.c @@ -601,7 +601,7 @@ int pt_pirq_iterate(struct domain *d, unsigned int pirq = 0, n, i; struct pirq *pirqs[8]; - ASSERT(spin_is_locked(&d->event_lock)); + rcu_read_lock(&d->pirq_rcu_lock); do { n = radix_tree_gang_lookup(&d->pirq_tree, (void **)pirqs, pirq, @@ -610,12 +610,18 @@ int pt_pirq_iterate(struct domain *d, { struct hvm_pirq_dpci *pirq_dpci = pirq_dpci(pirqs[i]); + spin_lock(&pirq_dpci->lock); + pirq = pirqs[i]->pirq; if ( (pirq_dpci->flags & HVM_IRQ_DPCI_MAPPED) ) rc = cb(d, pirq_dpci, arg); + + spin_unlock(&pirq_dpci->lock); } } while ( !rc && ++pirq < d->nr_pirqs && n == ARRAY_SIZE(pirqs) ); + rcu_read_unlock(&d->pirq_rcu_lock); + return rc; } @@ -678,9 +684,7 @@ void hvm_dpci_msi_eoi(struct domain *d, int vector) if ( !iommu_enabled || !d->arch.hvm_domain.irq.dpci ) return; - spin_lock(&d->event_lock); pt_pirq_iterate(d, _hvm_dpci_msi_eoi, (void *)(long)vector); - spin_unlock(&d->event_lock); } static void hvm_dirq_assist(struct domain *d, struct hvm_pirq_dpci *pirq_dpci) diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index 3729b0f..ae98c1e 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -355,6 +355,7 @@ struct domain */ struct radix_tree_root pirq_tree; unsigned int nr_pirqs; + rcu_read_lock_t pirq_rcu_lock; enum guest_type guest_type; -- 2.1.4