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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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?


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