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

Jürgen Groß
2020-08-24T05:09:40Z

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@linutronix.de>
> ---
> 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