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    Subject[PATCH 4.19 533/639] irqdomain: Add the missing assignment of domain->fwnode for named fwnode
    Date
    From: Dexuan Cui <decui@microsoft.com>

    [ Upstream commit 711419e504ebd68c8f03656616829c8ad7829389 ]

    Recently device pass-through stops working for Linux VM running on Hyper-V.

    git-bisect shows the regression is caused by the recent commit
    467a3bb97432 ("PCI: hv: Allocate a named fwnode ..."), but the root cause
    is that the commit d59f6617eef0 forgets to set the domain->fwnode for
    IRQCHIP_FWNODE_NAMED*, and as a result:

    1. The domain->fwnode remains to be NULL.

    2. irq_find_matching_fwspec() returns NULL since "h->fwnode == fwnode" is
    false, and pci_set_bus_msi_domain() sets the Hyper-V PCI root bus's
    msi_domain to NULL.

    3. When the device is added onto the root bus, the device's dev->msi_domain
    is set to NULL in pci_set_msi_domain().

    4. When a device driver tries to enable MSI-X, pci_msi_setup_msi_irqs()
    calls arch_setup_msi_irqs(), which uses the native MSI chip (i.e.
    arch/x86/kernel/apic/msi.c: pci_msi_controller) to set up the irqs, but
    actually pci_msi_setup_msi_irqs() is supposed to call
    msi_domain_alloc_irqs() with the hbus->irq_domain, which is created in
    hv_pcie_init_irq_domain() and is associated with the Hyper-V chip
    hv_msi_irq_chip. Consequently, the irq line is not properly set up, and
    the device driver can not receive any interrupt.

    Fixes: d59f6617eef0 ("genirq: Allow fwnode to carry name information only")
    Fixes: 467a3bb97432 ("PCI: hv: Allocate a named fwnode instead of an address-based one")
    Reported-by: Lili Deng <v-lide@microsoft.com>
    Signed-off-by: Dexuan Cui <decui@microsoft.com>
    Signed-off-by: Marc Zyngier <maz@kernel.org>
    Link: https://lore.kernel.org/r/PU1P153MB01694D9AF625AC335C600C5FBFBE0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/irq/irqdomain.c | 1 +
    1 file changed, 1 insertion(+)

    diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
    index 0b90be3607249..6e8520a81dd86 100644
    --- a/kernel/irq/irqdomain.c
    +++ b/kernel/irq/irqdomain.c
    @@ -148,6 +148,7 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, int size,
    switch (fwid->type) {
    case IRQCHIP_FWNODE_NAMED:
    case IRQCHIP_FWNODE_NAMED_ID:
    + domain->fwnode = fwnode;
    domain->name = kstrdup(fwid->name, GFP_KERNEL);
    if (!domain->name) {
    kfree(domain);
    --
    2.20.1


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