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

[Stefano Stabellini]

On Thu, 20 Jun 2013, Zhenzhong Duan wrote:
> On 2013-06-05 20:50, Stefano Stabellini wrote:
> > On Wed, 5 Jun 2013, Zhenzhong Duan wrote:
> > > Stefano Stabellini wrote:
> > > 
> > > On Tue, 21 May 2013, Stefano Stabellini wrote:
> > >    
> > > On Tue, 21 May 2013, Konrad Rzeszutek Wilk wrote:
> > >      
> > > Looking at the hypervisor code I couldn't see anything obviously wrong.
> > >          
> > > I think the culprit is "physdev_unmap_pirq":
> > > 
> > >     if ( is_hvm_domain(d) )
> > >      {
> > >          spin_lock(&d->event_lock);
> > >          gdprintk(XENLOG_WARNING,"d%d, pirq: %d is %x %s, irq: %d\n",
> > >              d->domain_id, pirq, domain_pirq_to_emuirq(d, pirq),
> > >              domain_pirq_to_emuirq(d, pirq) == IRQ_UNBOUND ? "unbound" :
> > > "",
> > >              domain_pirq_to_irq(d, pirq));
> > >                                                                                           if
> > > ( domain_pirq_to_emuirq(d, pirq) != IRQ_UNBOUND )
> > >              ret = unmap_domain_pirq_emuirq(d, pirq);
> > >          spin_unlock(&d->event_lock);
> > >          if ( domid == DOMID_SELF || ret )
> > >              goto free_domain;
> > > 
> > > It always tells me unbound:
> > > 
> > > (XEN) physdev.c:237:d14 14, pirq: 54 is ffffffff
> > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > (XEN) physdev.c:237:d14 14, pirq: 53 is ffffffff
> > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > (XEN) physdev.c:237:d14 14, pirq: 52 is ffffffff
> > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > (XEN) physdev.c:237:d14 14, pirq: 51 is ffffffff
> > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > (XEN) physdev.c:237:d14 14, pirq: 50 is ffffffff
> > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > (a bit older debug code, so the 'unbound' does not show up here).
> > > 
> > > Which means that the call to unmap_domain_pirq_emuirq does not happen.
> > > The checks in unmap_domain_pirq_emuirq also look to be depend
> > > on the code being IRQ_UNBOUND.
> > > 
> > > In other words, all of that code looks to only clear things when
> > > they are !IRQ_UNBOUND.
> > > 
> > > But the other logic (IRQ_UNBOUND) looks to be missing a removal
> > > in the radix tree:
> > > 
> > >    if ( emuirq != IRQ_PT )
> > >          radix_tree_delete(&d->arch.hvm_domain.emuirq_pirq, emuirq);
> > >                                                                          And
> > > I think that is what is causing the leak - the radix tree
> > > needs to be pruned? Or perhaps the allocate_pirq should check
> > > the radix tree for IRQ_UNBOUND ones and re-use them?
> > >        
> > > I think that you are looking in the wrong place.
> > > The issue is that QEMU doesn't call pt_msi_disable in
> > > pt_msgctrl_reg_write if (!val & PCI_MSI_FLAGS_ENABLE).
> > > 
> > > The code above is correct as is because it is trying to handle emulated
> > > IRQs and MSIs, not real passthrough MSIs. They latter are not added to
> > > that radix tree, see physdev_hvm_map_pirq and physdev_map_pirq.
> > >      
> > > 
> > > This patch fixes the issue, I have only tested MSI (MSI-X completely
> > > untested).
> > > 
> > > 
> > > diff --git a/hw/pass-through.c b/hw/pass-through.c
> > > index 304c438..079e465 100644
> > > --- a/hw/pass-through.c
> > > +++ b/hw/pass-through.c
> > > @@ -3866,7 +3866,11 @@ static int pt_msgctrl_reg_write(struct pt_dev
> > > *ptdev,
> > >           ptdev->msi->flags |= PCI_MSI_FLAGS_ENABLE;
> > >       }
> > >       else
> > > -        ptdev->msi->flags &= ~PCI_MSI_FLAGS_ENABLE;
> > > +    {
> > > +        if (ptdev->msi->flags & PT_MSI_MAPPED) {
> > > +            pt_msi_disable(ptdev);
> > > +        }
> > > +    }
> > >         /* pass through MSI_ENABLE bit when no MSI-INTx translation */
> > >       if (!ptdev->msi_trans_en) {
> > > @@ -4013,6 +4017,8 @@ static int pt_msixctrl_reg_write(struct pt_dev
> > > *ptdev,
> > >               pt_disable_msi_translate(ptdev);
> > >           }
> > >           pt_msix_update(ptdev);
> > > +    } else if (!(*value & PCI_MSIX_ENABLE) && ptdev->msix->enabled) {
> > > +        pt_msix_delete(ptdev);
> > >    
> > > Hi Stefano,
> > > I made a test with this patch, os reboot when driver reload. If use
> > > pt_msix_disable
> > > instead of pt_msix_delete, driver could be reloaded.
> > > But I still see some error in qemu.log and xen console. Seems four IRQs
> > > are not freed
> > > when unmap.
> > > --------------first load---------------------------
> > > pt_msix_update_one: pt_msix_update_one requested pirq = 103
> > > pt_msix_update_one: Update msix entry 0 with pirq 67 gvec 0
> > > pt_msix_update_one: pt_msix_update_one requested pirq = 102
> > > pt_msix_update_one: Update msix entry 1 with pirq 66 gvec 0
> > > pt_msix_update_one: pt_msix_update_one requested pirq = 101
> > > pt_msix_update_one: Update msix entry 2 with pirq 65 gvec 0
> > > pt_msix_update_one: pt_msix_update_one requested pirq = 100
> > > pt_msix_update_one: Update msix entry 3 with pirq 64 gvec 0
> > > ------------- first unload---------------------------
> > > pt_msix_disable: Unbind msix with pirq 67, gvec 0
> > > pt_msix_disable: Unmap msix with pirq 67
> > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > pt_msix_disable: Unbind msix with pirq 66, gvec 0
> > > pt_msix_disable: Unmap msix with pirq 66
> > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > pt_msix_disable: Unbind msix with pirq 65, gvec 0
> > > pt_msix_disable: Unmap msix with pirq 65
> > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > pt_msix_disable: Unbind msix with pirq 64, gvec 0
> > > pt_msix_disable: Unmap msix with pirq 64
> > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > Can you add some printks in Xen (the hypercall name is
> > PHYSDEVOP_unmap_pirq) to figure out exactly why they are failing?
> Did some test, domain_pirq_to_emuirq(d, unmap->pirq) = IRQ_UNBOUND in
> physdev_unmap_pirq.

That means that Linux didn't call irq_enable on the MSI-X in question:

irq_enable -> __startup_pirq -> EVTCHNOP_bind_pirq

EVTCHNOP_bind_pirq is implemented by evtchn_bind_pirq in Xen and calls
map_domain_emuirq_pirq, so domain_pirq_to_emuirq(d, unmap->pirq) should
be IRQ_PT.

I don't know if that's a normal condition, but in any case it should
not create any problems to physdev_unmap_pirq, in fact the folloing
check:

    if ( domid == DOMID_SELF || ret )
            goto free_domain;

should fail so Xen should continue and execute unmap_domain_pirq. That's
what we want.
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