Re: [Xen-devel] [PATCH] xen: reuse the same pirq allocated when driver load first time

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

> > Hi Stefano,
> > 
> > do you work out a patch for me to test?
> 
> I'll be traveling/busy for a few weeks, maybe it's best if someone else
> picks up this work item.

This little test-case below should have worked:

#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <xen/xen.h>
#include <xen/page.h>
#include <asm/xen/hypervisor.h>
#include <xen/features.h>
#include <xen/events.h>

MODULE_AUTHOR("Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>");
MODULE_DESCRIPTION("alloc_and_unmap");
MODULE_LICENSE("GPL");
MODULE_VERSION("0.1");

static int do_it(void)
{
        struct physdev_get_free_pirq op_get_free_pirq;
        struct physdev_unmap_pirq unmap_irq;
        int rc, pirq;

        op_get_free_pirq.type = MAP_PIRQ_TYPE_MSI;
        rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
        if (rc) {
                printk(KERN_WARNING "%s:%d rc:%d\n", __func__, __LINE__, rc);
                return rc;
        }
        pirq = op_get_free_pirq.pirq;
        unmap_irq.pirq = pirq;
        unmap_irq.domid = DOMID_SELF;
        rc = HYPERVISOR_physdev_op(PHYSDEVOP_unmap_pirq, &unmap_irq);
        if (rc) {
                printk(KERN_WARNING "unmap irq failed %d\n", rc);
                return rc;
        }
        printk("PIRQ: %d\n", pirq);
        return 0;
}
static int __init alloc_and_unmap_init(void)
{
        int i;

        for (i = 0; i < 10; i++)
                if (do_it())
                        break;
        return 0;
}
static void __exit alloc_and_unmap_exit(void)
{
}
module_init(alloc_and_unmap_init);
module_exit(alloc_and_unmap_exit);


But I get:

# insmod /alloc_and_unmap.ko 
[   34.899277] PIRQ: 55
[   34.901846] PIRQ: 54
[   34.904351] PIRQ: 53
[   34.906921] PIRQ: 52
[   34.909451] PIRQ: 51
[   34.912038] PIRQ: 50
[   34.914650] PIRQ: 49
[   34.917205] PIRQ: 48
[   34.919776] PIRQ: 47
[   34.922339] PIRQ: 46

Which means there is some bug in the hypervisor as well (This is with Xen 4.3
and traditional QEMU - not that it matters as I am just doing these hypercalls).


At this point I think that upstream option is to save the PIRQ value and re-use 
it.
Will post a patch for it.

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