have architectures specify the number of PIRQs a hardware domain gets

The current value of nr_static_irqs + 256 is often too small for larger
systems. Make it dependent on CPU count and number of IO-APIC pins on
x86, and (until it obtains PCI support) simply NR_IRQS on ARM.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Release-Acked-by: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>

docs/misc/xen-command-line.markdown

@@ -596,13 +596,16 @@ Force or disable use of EFI runtime services.
 ### extra\_guest\_irqs
 > `= [<domU number>][,<dom0 number>]`
 
-> Default: `32,256`
+> Default: `32,<variable>`
 
 Change the number of PIRQs available for guests.  The optional first number is
 common for all domUs, while the optional second number (preceded by a comma)
 is for dom0.  Changing the setting for domU has no impact on dom0 and vice
 versa.  For example to change dom0 without changing domU, use
-`extra_guest_irqs=,512`
+`extra_guest_irqs=,512`.  The default value for Dom0 and an eventual separate
+hardware domain is architecture dependent.
+Note that specifying zero as domU value means zero, while for dom0 it means
+to use the default.
 
 ### flask\_enabled
 > `= <integer>`

xen/arch/x86/domain_build.c

@@ -101,7 +101,7 @@ static void __init parse_dom0_max_vcpus(const char *s)
 }
 custom_param("dom0_max_vcpus", parse_dom0_max_vcpus);
 
-struct vcpu *__init alloc_dom0_vcpu0(struct domain *dom0)
+unsigned int __init dom0_max_vcpus(void)
 {
     unsigned max_vcpus;
 
@@ -113,6 +113,13 @@ struct vcpu *__init alloc_dom0_vcpu0(struct domain *dom0)
     if ( max_vcpus > MAX_VIRT_CPUS )
         max_vcpus = MAX_VIRT_CPUS;
 
+    return max_vcpus;
+}
+
+struct vcpu *__init alloc_dom0_vcpu0(struct domain *dom0)
+{
+    unsigned int max_vcpus = dom0_max_vcpus();
+
     dom0->vcpu = xzalloc_array(struct vcpu *, max_vcpus);
     if ( !dom0->vcpu )
         return NULL;

xen/arch/x86/io_apic.c

@@ -33,6 +33,7 @@
 #include <asm/smp.h>
 #include <asm/desc.h>
 #include <asm/msi.h>
+#include <asm/setup.h>
 #include <mach_apic.h>
 #include <io_ports.h>
 #include <public/physdev.h>
@@ -2606,3 +2607,14 @@ void __init init_ioapic_mappings(void)
            nr_irqs_gsi, nr_irqs - nr_irqs_gsi);
 }
 
+unsigned int arch_hwdom_irqs(domid_t domid)
+{
+    unsigned int n = fls(num_present_cpus());
+
+    if ( !domid )
+        n = min(n, dom0_max_vcpus());
+    n = min(nr_irqs_gsi + n * NR_DYNAMIC_VECTORS, nr_irqs);
+    printk("Dom%d has maximum %u PIRQs\n", domid, n);
+
+    return n;
+}

xen/common/domain.c

@@ -231,14 +231,14 @@ static int late_hwdom_init(struct domain *d)
 #endif
 }
 
-static unsigned int __read_mostly extra_dom0_irqs = 256;
+static unsigned int __read_mostly extra_hwdom_irqs;
 static unsigned int __read_mostly extra_domU_irqs = 32;
 static void __init parse_extra_guest_irqs(const char *s)
 {
     if ( isdigit(*s) )
         extra_domU_irqs = simple_strtoul(s, &s, 0);
     if ( *s == ',' && isdigit(*++s) )
-        extra_dom0_irqs = simple_strtoul(s, &s, 0);
+        extra_hwdom_irqs = simple_strtoul(s, &s, 0);
 }
 custom_param("extra_guest_irqs", parse_extra_guest_irqs);
 
@@ -326,7 +326,8 @@ struct domain *domain_create(
         if ( !is_hardware_domain(d) )
             d->nr_pirqs = nr_static_irqs + extra_domU_irqs;
         else
-            d->nr_pirqs = nr_static_irqs + extra_dom0_irqs;
+            d->nr_pirqs = extra_hwdom_irqs ? nr_static_irqs + extra_hwdom_irqs
+                                           : arch_hwdom_irqs(domid);
         if ( d->nr_pirqs > nr_irqs )
             d->nr_pirqs = nr_irqs;
 

xen/include/asm-arm/irq.h

@@ -21,10 +21,10 @@ struct arch_irq_desc {
 
 #define NR_LOCAL_IRQS	32
 #define NR_IRQS		1024
-#define nr_irqs NR_IRQS
 
 #define nr_irqs NR_IRQS
 #define nr_static_irqs NR_IRQS
+#define arch_hwdom_irqs(domid) NR_IRQS
 
 struct irq_desc;
 struct irqaction;

xen/include/asm-x86/setup.h

@@ -35,6 +35,8 @@ int construct_dom0(
 unsigned long initial_images_nrpages(void);
 void discard_initial_images(void);
 
+unsigned int dom0_max_vcpus(void);
+
 int xen_in_range(unsigned long mfn);
 
 void microcode_grab_module(

xen/include/xen/irq.h

@@ -168,4 +168,8 @@ static inline void set_native_irq_info(unsigned int irq, const cpumask_t *mask)
 
 unsigned int set_desc_affinity(struct irq_desc *, const cpumask_t *);
 
+#ifndef arch_hwdom_irqs
+unsigned int arch_hwdom_irqs(domid_t);
+#endif
+
 #endif /* __XEN_IRQ_H__ */