linux-kernel - [PATCH] ACPI / PCI: Bail early in acpi_pci_add

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Date:   Thu, 14 Sep 2017 16:50:14 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jork Loeser <jloeser@...rosoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: [PATCH] ACPI / PCI: Bail early in acpi_pci_add_bus() if there is no ACPI handle

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() with 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@...hat.com>
---
 drivers/pci/pci-acpi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index a8da543b3814..4708eb9df71b 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -624,7 +624,7 @@ void acpi_pci_add_bus(struct pci_bus *bus)
 	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);
-- 
2.13.5