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@xxxxxxxxxxxxx>
Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
---
Note: the commit 467a3bb97432 ("PCI: hv: Allocate a named fwnode ...") has not
gone in Linus's tree yet (the commit is in linux-next for a while), so the commit ID
in the changelog can change when it goes in Linus's tree.
This patch works in my test, but I'm not 100% sure this is the right fix.
Looking forward to your comment!
kernel/irq/irqdomain.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index e7bbab149750..132672b74e4b 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -149,6 +149,7 @@ 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);
--
2.19.1
