| Message ID | 1606960706-21274-2-git-send-email-igor.druzhinin@citrix.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2,1/2] x86/IRQ: make max number of guests for a shared IRQ configurable | expand |
On 03.12.2020 02:58, Igor Druzhinin wrote: > @@ -1540,6 +1540,7 @@ int pirq_guest_bind(struct vcpu *v, struct pirq *pirq, int will_share) > unsigned int irq; > struct irq_desc *desc; > irq_guest_action_t *action, *newaction = NULL; > + unsigned int max_nr_guests = will_share ? irq_max_guests : 1; > int rc = 0; > > WARN_ON(!spin_is_locked(&v->domain->event_lock)); > @@ -1571,7 +1572,7 @@ int pirq_guest_bind(struct vcpu *v, struct pirq *pirq, int will_share) > { > spin_unlock_irq(&desc->lock); > if ( (newaction = xmalloc_bytes(sizeof(irq_guest_action_t) + > - irq_max_guests * sizeof(action->guest[0]))) != NULL && > + max_nr_guests * sizeof(action->guest[0]))) != NULL && > zalloc_cpumask_var(&newaction->cpu_eoi_map) ) > goto retry; > xfree(newaction); > @@ -1640,7 +1641,7 @@ int pirq_guest_bind(struct vcpu *v, struct pirq *pirq, int will_share) > goto retry; > } > > - if ( action->nr_guests == irq_max_guests ) > + if ( action->nr_guests == max_nr_guests ) > { > printk(XENLOG_G_INFO "Cannot bind IRQ%d to dom%d. " > "Already at max share %u, increase with irq_max_guests= option.\n", Just as a minor remark - I don't think this last hunk is necessary, as the !will_share case won't make it here unless action->nr_guests is still zero. At which point the need for the new local variable would also disappear. But I'm not going to insist, as there may be the view that the code is more clear this way. However, if clarity (in the sense of "obviously correct") is the goal, then I think using >= instead of == would now become preferable. Jan
diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc index f5f230c..dea2a22 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -1644,7 +1644,7 @@ This option is ignored in **pv-shim** mode. ### irq_max_guests (x86) > `= <integer>` -> Default: `16` +> Default: `32` Maximum number of guests IRQ could be shared between, i.e. a limit on the number of guests it is possible to start each having assigned a device diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c index 5ae9846..70b7a53 100644 --- a/xen/arch/x86/irq.c +++ b/xen/arch/x86/irq.c @@ -440,7 +440,7 @@ int __init init_irq_data(void) irq_to_desc(irq)->irq = irq; if ( !irq_max_guests || irq_max_guests > 255) - irq_max_guests = 16; + irq_max_guests = 32; #ifdef CONFIG_PV /* Never allocate the hypercall vector or Linux/BSD fast-trap vector. */ @@ -1540,6 +1540,7 @@ int pirq_guest_bind(struct vcpu *v, struct pirq *pirq, int will_share) unsigned int irq; struct irq_desc *desc; irq_guest_action_t *action, *newaction = NULL; + unsigned int max_nr_guests = will_share ? irq_max_guests : 1; int rc = 0; WARN_ON(!spin_is_locked(&v->domain->event_lock)); @@ -1571,7 +1572,7 @@ int pirq_guest_bind(struct vcpu *v, struct pirq *pirq, int will_share) { spin_unlock_irq(&desc->lock); if ( (newaction = xmalloc_bytes(sizeof(irq_guest_action_t) + - irq_max_guests * sizeof(action->guest[0]))) != NULL && + max_nr_guests * sizeof(action->guest[0]))) != NULL && zalloc_cpumask_var(&newaction->cpu_eoi_map) ) goto retry; xfree(newaction); @@ -1640,7 +1641,7 @@ int pirq_guest_bind(struct vcpu *v, struct pirq *pirq, int will_share) goto retry; } - if ( action->nr_guests == irq_max_guests ) + if ( action->nr_guests == max_nr_guests ) { printk(XENLOG_G_INFO "Cannot bind IRQ%d to dom%d. " "Already at max share %u, increase with irq_max_guests= option.\n",
... and increase default "irq_max_guests" to 32. It's not necessary to have an array of a size more than 1 for non-shareable IRQs and it might impact scalability in case of high "irq_max_guests" values being used - every IRQ in the system including MSIs would be supplied with an array of that size. Since it's now less impactful to use higher "irq_max_guests" value - bump the default to 32. That should give more headroom for future systems. Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> --- New in v2. This is suggested by Jan and is optional for me. --- docs/misc/xen-command-line.pandoc | 2 +- xen/arch/x86/irq.c | 7 ++++--- 2 files changed, 5 insertions(+), 4 deletions(-)