Re: [patch RFC 23/38] x86/xen: Rework MSI teardown

[Jürgen Groß <jgross@xxxxxxxx>]

On 21.08.20 02:24, Thomas Gleixner wrote:
> X86 cannot store the irq domain pointer in struct device without breaking
> XEN because the irq domain pointer takes precedence over arch_*_msi_irqs()
> fallbacks.
>
> XENs MSI teardown relies on default_teardown_msi_irqs() which invokes
> arch_teardown_msi_irq(). default_teardown_msi_irqs() is a trivial iterator
> over the msi entries associated to a device.
>
> Implement this loop in xen_teardown_msi_irqs() to prepare for removal of
> the fallbacks for X86.
>
> This is a preparatory step to wrap XEN MSI alloc/free into a irq domain
> which in turn allows to store the irq domain pointer in struct device and
> to use the irq domain functions directly.
>
> Signed-off-by: Thomas Gleixner<tglx@xxxxxxxxxxxxx>
> ---
>   arch/x86/pci/xen.c |   23 ++++++++++++++++++-----
>   1 file changed, 18 insertions(+), 5 deletions(-)
>
> --- a/arch/x86/pci/xen.c
> +++ b/arch/x86/pci/xen.c
> @@ -376,20 +376,31 @@ static void xen_initdom_restore_msi_irqs
>   static void xen_teardown_msi_irqs(struct pci_dev *dev)
>   {
>         struct msi_desc *msidesc;
> +       int i;
> +
> +       for_each_pci_msi_entry(msidesc, dev) {
> +               if (msidesc->irq) {
> +                       for (i = 0; i < msidesc->nvec_used; i++)
> +                               xen_destroy_irq(msidesc->irq + i);
> +               }
> +       }
> +}
> +
> +static void xen_pv_teardown_msi_irqs(struct pci_dev *dev)
> +{
> +       struct msi_desc *msidesc = first_pci_msi_entry(dev);
>   
> -	msidesc = first_pci_msi_entry(dev);
>         if (msidesc->msi_attrib.is_msix)
>                 xen_pci_frontend_disable_msix(dev);
>         else
>                 xen_pci_frontend_disable_msi(dev);
>   
> -	/* Free the IRQ's and the msidesc using the generic code. */
> -       default_teardown_msi_irqs(dev);
> +       xen_teardown_msi_irqs(dev);
>   }
>   
>   static void xen_teardown_msi_irq(unsigned int irq)
>   {
> -       xen_destroy_irq(irq);
> +       WARN_ON_ONCE(1);
>   }
>   
>   #endif
> @@ -412,7 +423,7 @@ int __init pci_xen_init(void)
>   #ifdef CONFIG_PCI_MSI
>         x86_msi.setup_msi_irqs = xen_setup_msi_irqs;
>         x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
> -       x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
> +       x86_msi.teardown_msi_irqs = xen_pv_teardown_msi_irqs;
>         pci_msi_ignore_mask = 1;
>   #endif
>         return 0;
> @@ -436,6 +447,7 @@ static void __init xen_hvm_msi_init(void
>         }
>   
>   	x86_msi.setup_msi_irqs = xen_hvm_setup_msi_irqs;
> +       x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
>         x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
>   }
>   #endif
> @@ -472,6 +484,7 @@ int __init pci_xen_initial_domain(void)
>   #ifdef CONFIG_PCI_MSI
>         x86_msi.setup_msi_irqs = xen_initdom_setup_msi_irqs;
>         x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
> +       x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
This should be xen_pv_teardown_msi_irqs, as pci_xen_initial_domain() is
called only for the pv initial domain case today.

>         x86_msi.restore_msi_irqs = xen_initdom_restore_msi_irqs;
>         pci_msi_ignore_mask = 1;
>   #endif

Juergen