From aaca49642b92c8a57d3ca5029a5a94019c7af69f Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Fri, 20 Aug 2010 18:57:53 -0700 Subject: [PATCH 1/2] xen: use percpu interrupts for IPIs and VIRQs IPIs and VIRQs are inherently per-cpu event types, so treat them as such: - use a specific percpu irq_chip implementation, and - handle them with handle_percpu_irq This makes the path for delivering these interrupts more efficient (no masking/unmasking, no locks), and it avoid problems with attempts to migrate them. Signed-off-by: Jeremy Fitzhardinge Cc: Stable Kernel --- drivers/xen/events.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/drivers/xen/events.c b/drivers/xen/events.c index 72f91bff29c7..0923ccb26121 100644 --- a/drivers/xen/events.c +++ b/drivers/xen/events.c @@ -112,6 +112,7 @@ static inline unsigned long *cpu_evtchn_mask(int cpu) #define VALID_EVTCHN(chn) ((chn) != 0) static struct irq_chip xen_dynamic_chip; +static struct irq_chip xen_percpu_chip; /* Constructor for packed IRQ information. */ static struct irq_info mk_unbound_info(void) @@ -403,8 +404,8 @@ static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu) if (irq < 0) goto out; - set_irq_chip_and_handler_name(irq, &xen_dynamic_chip, - handle_level_irq, "ipi"); + set_irq_chip_and_handler_name(irq, &xen_percpu_chip, + handle_percpu_irq, "ipi"); bind_ipi.vcpu = cpu; if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi, @@ -444,8 +445,8 @@ static int bind_virq_to_irq(unsigned int virq, unsigned int cpu) irq = find_unbound_irq(); - set_irq_chip_and_handler_name(irq, &xen_dynamic_chip, - handle_level_irq, "virq"); + set_irq_chip_and_handler_name(irq, &xen_percpu_chip, + handle_percpu_irq, "virq"); evtchn_to_irq[evtchn] = irq; irq_info[irq] = mk_virq_info(evtchn, virq); @@ -964,6 +965,16 @@ static struct irq_chip xen_dynamic_chip __read_mostly = { .retrigger = retrigger_dynirq, }; +static struct irq_chip xen_percpu_chip __read_mostly = { + .name = "xen-percpu", + + .disable = disable_dynirq, + .mask = disable_dynirq, + .unmask = enable_dynirq, + + .ack = ack_dynirq, +}; + int xen_set_callback_via(uint64_t via) { struct xen_hvm_param a; From dffe2e1e1a1ddb566a76266136c312801c66dcf7 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Fri, 20 Aug 2010 19:10:01 -0700 Subject: [PATCH 2/2] xen: handle events as edge-triggered Xen events are logically edge triggered, as Xen only calls the event upcall when an event is newly set, but not continuously as it remains set. As a result, use handle_edge_irq rather than handle_level_irq. This has the important side-effect of fixing a long-standing bug of events getting lost if: - an event's interrupt handler is running - the event is migrated to a different vcpu - the event is re-triggered The most noticable symptom of these lost events is occasional lockups of blkfront. Many thanks to Tom Kopec and Daniel Stodden in tracking this down. Signed-off-by: Jeremy Fitzhardinge Cc: Tom Kopec Cc: Daniel Stodden Cc: Stable Kernel --- drivers/xen/events.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/xen/events.c b/drivers/xen/events.c index 0923ccb26121..13365ba35218 100644 --- a/drivers/xen/events.c +++ b/drivers/xen/events.c @@ -378,7 +378,7 @@ int bind_evtchn_to_irq(unsigned int evtchn) irq = find_unbound_irq(); set_irq_chip_and_handler_name(irq, &xen_dynamic_chip, - handle_level_irq, "event"); + handle_edge_irq, "event"); evtchn_to_irq[evtchn] = irq; irq_info[irq] = mk_evtchn_info(evtchn);