4.4-stable review patch. If anyone has any objections, please let me know.
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From: Vitaly Kuznetsov vkuznets@redhat.com
commit a0040c0145945d3bd203df8fa97f6dfa819f3f7d upstream.
Hyper-V instances support PCI pass-through which is implemented through PV pci-hyperv driver. When a device is passed through, a new root PCI bus is created in the guest. The bus sits on top of VMBus and has no associated information in ACPI. acpi_pci_add_bus() in this case proceeds all the way to acpi_evaluate_dsm(), which reports
ACPI: : failed to evaluate _DSM (0x1001)
While acpi_pci_slot_enumerate() and acpiphp_enumerate_slots() are protected against ACPI_HANDLE() being NULL and do nothing, acpi_evaluate_dsm() is not and gives us the error. It seems the correct fix is to not do anything in acpi_pci_add_bus() in such cases.
Signed-off-by: Vitaly Kuznetsov vkuznets@redhat.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Cc: Sinan Kaya okaya@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/pci/pci-acpi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/pci/pci-acpi.c +++ b/drivers/pci/pci-acpi.c @@ -543,7 +543,7 @@ void acpi_pci_add_bus(struct pci_bus *bu union acpi_object *obj; struct pci_host_bridge *bridge;
- if (acpi_pci_disabled || !bus->bridge) + if (acpi_pci_disabled || !bus->bridge || !ACPI_HANDLE(bus->bridge)) return;
acpi_pci_slot_enumerate(bus);