# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1281707943 -3600
# Node ID fe21e474c6942a95fa0f86bd65e1209c6010ed33
# Parent 3cee41690fa26853acb0be65065c52f6029ca599
x86: eliminate bogus IRQ restrictions
As pointed out in
http://lists.xensource.com/archives/html/xen-devel/2010-07/msg00077.html
the limits introduced in c/s 20072 are at least
questionable. Eliminate them in favor of a more dynamic approach:
There's no real need for an upper limit on nr_irqs (as anything beyond
nr_irqs_gsi isn't visible to domains anyway), and the split point (and
hence ratio) between GSI and MSI/MSI-X IRQs doesn't need to be hard
coded, but can instead be controlled on the command line in case there
are *very* many GSIs.
The default used for nr_irqs will be rather large with this patch, so
it may not be acceptable without also switching to a sparse irq_desc[]
as was done not so lomg ago in Linux.
The added capping of any domain's nr_pirqs is based on the observation
that no domain can possibly have more than the system wide number of
IRQs. The opposite case may in fact also require some adjustment:
Defaulting the number of non-GSI IRQs available (namely to Dom0) to a
fixed value may not be the best choice going forward, since if there
indeed are very many non-GSI interrupt sources, it won't be possible
for the kernel to make use of them without giving
"extra_guest_irqs=" on the command line (but the goal should be to
allow things to work right by default even on large systems).
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---
xen/arch/x86/io_apic.c | 47 +++++++++++++++++++++++++++++++++-------------
xen/arch/x86/irq.c | 2 -
xen/common/domain.c | 2 +
xen/include/asm-x86/irq.h | 3 --
4 files changed, 37 insertions(+), 17 deletions(-)
diff -r 3cee41690fa2 -r fe21e474c694 xen/arch/x86/io_apic.c
--- a/xen/arch/x86/io_apic.c Fri Aug 13 14:58:06 2010 +0100
+++ b/xen/arch/x86/io_apic.c Fri Aug 13 14:59:03 2010 +0100
@@ -2503,6 +2503,9 @@ void dump_ioapic_irq_info(void)
unsigned highest_gsi(void);
+static unsigned int __initdata max_gsi_irqs;
+integer_param("max_gsi_irqs", max_gsi_irqs);
+
void __init init_ioapic_mappings(void)
{
unsigned long ioapic_phys;
@@ -2547,19 +2550,37 @@ void __init init_ioapic_mappings(void)
nr_irqs_gsi = max(nr_irqs_gsi, highest_gsi());
+ if ( max_gsi_irqs == 0 )
+ max_gsi_irqs = nr_irqs ? nr_irqs / 8 : PAGE_SIZE;
+ else if ( nr_irqs != 0 && max_gsi_irqs > nr_irqs )
+ {
+ printk(XENLOG_WARNING "\"max_gsi_irqs=\" cannot be specified larger"
+ " than \"nr_irqs=\"\n");
+ max_gsi_irqs = nr_irqs;
+ }
+ if ( max_gsi_irqs < 16 )
+ max_gsi_irqs = 16;
+
+ /* for PHYSDEVOP_pirq_eoi_gmfn guest assumptions */
+ if ( max_gsi_irqs > PAGE_SIZE * 8 )
+ max_gsi_irqs = PAGE_SIZE * 8;
+
if ( !smp_found_config || skip_ioapic_setup || nr_irqs_gsi < 16 )
nr_irqs_gsi = 16;
- else if ( nr_irqs_gsi > MAX_GSI_IRQS)
+ else if ( nr_irqs_gsi > max_gsi_irqs )
{
- /* for PHYSDEVOP_pirq_eoi_gmfn guest assumptions */
- printk(KERN_WARNING "Limiting number of GSI IRQs found (%u) to %lu\n",
- nr_irqs_gsi, MAX_GSI_IRQS);
- nr_irqs_gsi = MAX_GSI_IRQS;
- }
-
- if (nr_irqs < 2 * nr_irqs_gsi)
- nr_irqs = 2 * nr_irqs_gsi;
-
- if (nr_irqs > MAX_NR_IRQS)
- nr_irqs = MAX_NR_IRQS;
-}
+ printk(XENLOG_WARNING "Limiting to %u GSI IRQs (found %u)\n",
+ max_gsi_irqs, nr_irqs_gsi);
+ nr_irqs_gsi = max_gsi_irqs;
+ }
+
+ if ( nr_irqs == 0 )
+ nr_irqs = cpu_has_apic ?
+ max(16U + num_present_cpus() * NR_DYNAMIC_VECTORS,
+ 8 * nr_irqs_gsi) :
+ nr_irqs_gsi;
+ else if ( nr_irqs < 16 )
+ nr_irqs = 16;
+ printk(XENLOG_INFO "IRQ limits: %u GSI, %u MSI/MSI-X\n",
+ nr_irqs_gsi, nr_irqs - nr_irqs_gsi);
+}
diff -r 3cee41690fa2 -r fe21e474c694 xen/arch/x86/irq.c
--- a/xen/arch/x86/irq.c Fri Aug 13 14:58:06 2010 +0100
+++ b/xen/arch/x86/irq.c Fri Aug 13 14:59:03 2010 +0100
@@ -29,7 +29,7 @@ boolean_param("noirqbalance", opt_noirqb
boolean_param("noirqbalance", opt_noirqbalance);
unsigned int __read_mostly nr_irqs_gsi = 16;
-unsigned int __read_mostly nr_irqs = 1024;
+unsigned int __read_mostly nr_irqs;
integer_param("nr_irqs", nr_irqs);
u8 __read_mostly *irq_vector;
diff -r 3cee41690fa2 -r fe21e474c694 xen/common/domain.c
--- a/xen/common/domain.c Fri Aug 13 14:58:06 2010 +0100
+++ b/xen/common/domain.c Fri Aug 13 14:59:03 2010 +0100
@@ -274,6 +274,8 @@ struct domain *domain_create(
d->nr_pirqs = nr_irqs_gsi + extra_domU_irqs;
else
d->nr_pirqs = nr_irqs_gsi + extra_dom0_irqs;
+ if ( d->nr_pirqs > nr_irqs )
+ d->nr_pirqs = nr_irqs;
d->pirq_to_evtchn = xmalloc_array(u16, d->nr_pirqs);
d->pirq_mask = xmalloc_array(
diff -r 3cee41690fa2 -r fe21e474c694 xen/include/asm-x86/irq.h
--- a/xen/include/asm-x86/irq.h Fri Aug 13 14:58:06 2010 +0100
+++ b/xen/include/asm-x86/irq.h Fri Aug 13 14:59:03 2010 +0100
@@ -22,9 +22,6 @@
#define irq_to_desc(irq) (&irq_desc[irq])
#define irq_cfg(irq) (&irq_cfg[irq])
-
-#define MAX_GSI_IRQS PAGE_SIZE * 8
-#define MAX_NR_IRQS (2 * MAX_GSI_IRQS)
struct irq_cfg {
int vector;
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