From 89911501f3aae44a43984793341a3bf1f4c583c2 Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Thu, 3 Mar 2011 11:57:44 -0500 Subject: [PATCH] xen: events: allocate GSIs and dynamic IRQs from separate IRQ ranges. There are three cases which we need to care about, PV guest, PV domain 0 and HVM guest. The PV guest case is simple since it has no access to ACPI or real APICs and therefore has no GSIs therefore we simply dynamically allocate all IRQs. The potentially interesting case here is PIRQ type event channels associated with passed through PCI devices. However even in this case the guest has no direct interaction with the physical GSI since that happens in the PCI backend. The PV domain 0 and HVM guest cases are actually the same. In domain 0 case the kernel sees the host ACPI and GSIs (although it only sees the APIC indirectly via the hypervisor) and in the HVM guest case it sees the virtualised ACPI and emulated APICs. In these cases we start allocating dynamic IRQs at nr_irqs_gsi so that they cannot clash with any GSI. Currently xen_allocate_irq_dynamic starts at nr_irqs and works backwards looking for a free IRQ in order to (try and) avoid clashing with GSIs used in domain 0 and in HVM guests. This change avoids that although we retain the behaviour of allowing dynamic IRQs to encroach on the GSI range if no suitable IRQs are available since a future IRQ clash is deemed preferable to failure right now. Signed-off-by: Ian Campbell Signed-off-by: Konrad Rzeszutek Wilk Cc: Stefano Stabellini Cc: Jeremy Fitzhardinge --- drivers/xen/events.c | 81 ++++++++++++++++---------------------------- 1 file changed, 29 insertions(+), 52 deletions(-) diff --git a/drivers/xen/events.c b/drivers/xen/events.c index 81a53eb6cd1d..06f2e61de691 100644 --- a/drivers/xen/events.c +++ b/drivers/xen/events.c @@ -376,72 +376,49 @@ static void unmask_evtchn(int port) put_cpu(); } -static int get_nr_hw_irqs(void) -{ - int ret = 1; - -#ifdef CONFIG_X86_IO_APIC - ret = get_nr_irqs_gsi(); -#endif - - return ret; -} - static int xen_allocate_irq_dynamic(void) { - struct irq_data *data; - int irq, res; - int bottom = get_nr_hw_irqs(); - int top = nr_irqs-1; + int first = 0; + int irq; - if (bottom == nr_irqs) - goto no_irqs; - - /* This loop starts from the top of IRQ space and goes down. - * We need this b/c if we have a PCI device in a Xen PV guest - * we do not have an IO-APIC (though the backend might have them) - * mapped in. To not have a collision of physical IRQs with the Xen - * event channels start at the top of the IRQ space for virtual IRQs. +#ifdef CONFIG_X86_IO_APIC + /* + * For an HVM guest or domain 0 which see "real" (emulated or + * actual repectively) GSIs we allocate dynamic IRQs + * e.g. those corresponding to event channels or MSIs + * etc. from the range above those "real" GSIs to avoid + * collisions. */ - for (irq = top; irq > bottom; irq--) { - data = irq_get_irq_data(irq); - /* only 15->0 have init'd desc; handle irq > 16 */ - if (!data) - break; - if (data->chip == &no_irq_chip) - break; - if (data->chip != &xen_dynamic_chip) - continue; - if (irq_info[irq].type == IRQT_UNBOUND) - return irq; + if (xen_initial_domain() || xen_hvm_domain()) + first = get_nr_irqs_gsi(); +#endif + +retry: + irq = irq_alloc_desc_from(first, -1); + + if (irq == -ENOMEM && first > NR_IRQS_LEGACY) { + printk(KERN_ERR "Out of dynamic IRQ space and eating into GSI space. You should increase nr_irqs\n"); + first = max(NR_IRQS_LEGACY, first - NR_IRQS_LEGACY); + goto retry; } - if (irq == bottom) - goto no_irqs; - - res = irq_alloc_desc_at(irq, -1); - - if (WARN_ON(res != irq)) - return -1; + if (irq < 0) + panic("No available IRQ to bind to: increase nr_irqs!\n"); return irq; - -no_irqs: - panic("No available IRQ to bind to: increase nr_irqs!\n"); -} - -static bool identity_mapped_irq(unsigned irq) -{ - /* identity map all the hardware irqs */ - return irq < get_nr_hw_irqs(); } static int xen_allocate_irq_gsi(unsigned gsi) { int irq; - if (!identity_mapped_irq(gsi) && - (xen_initial_domain() || !xen_pv_domain())) + /* + * A PV guest has no concept of a GSI (since it has no ACPI + * nor access to/knowledge of the physical APICs). Therefore + * all IRQs are dynamically allocated from the entire IRQ + * space. + */ + if (xen_pv_domain() && !xen_initial_domain()) return xen_allocate_irq_dynamic(); /* Legacy IRQ descriptors are already allocated by the arch. */