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Subject[PATCH 4.4 09/12] ACPI / PCI: Bail early in acpi_pci_add_bus() if there is no ACPI handle
4.4-stable review patch.  If anyone has any objections, please let me know.


From: Vitaly Kuznetsov <>

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 <>
Signed-off-by: Bjorn Helgaas <>
Cc: Sinan Kaya <>
Signed-off-by: Greg Kroah-Hartman <>

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))


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