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    Subject[tip: x86/irq] x86/xen: Rework MSI teardown
    The following commit has been merged into the x86/irq branch of tip:

    Commit-ID: 7d4d892de6e74194fcfd4ff69f21ba3da97ae282
    Gitweb: https://git.kernel.org/tip/7d4d892de6e74194fcfd4ff69f21ba3da97ae282
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Wed, 26 Aug 2020 13:16:55 +02:00
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitterDate: Wed, 16 Sep 2020 16:52:36 +02:00

    x86/xen: Rework MSI teardown

    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>
    Reviewed-by: Juergen Gross <jgross@suse.com>
    Link: https://lore.kernel.org/r/20200826112333.326841410@linutronix.de

    ---
    arch/x86/pci/xen.c | 23 ++++++++++++++++++-----
    1 file changed, 18 insertions(+), 5 deletions(-)

    diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
    index ba8dc94..6a2debe 100644
    --- a/arch/x86/pci/xen.c
    +++ b/arch/x86/pci/xen.c
    @@ -377,20 +377,31 @@ static void xen_initdom_restore_msi_irqs(struct pci_dev *dev)
    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
    @@ -413,7 +424,7 @@ 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;
    @@ -437,6 +448,7 @@ 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
    @@ -473,6 +485,7 @@ 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_pv_msi_irqs;
    x86_msi.restore_msi_irqs = xen_initdom_restore_msi_irqs;
    pci_msi_ignore_mask = 1;
    #endif
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