PCI/sysfs: Protect driver's D3cold preference from user space

commit 70b70a4307cccebe91388337b1c85735ce4de6ff upstream.

struct pci_dev contains two flags which govern whether the device may
suspend to D3cold:

* no_d3cold provides an opt-out for drivers (e.g. if a device is known
  to not wake from D3cold)

* d3cold_allowed provides an opt-out for user space (default is true,
  user space may set to false)

Since commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend"),
the user space setting overwrites the driver setting.  Essentially user
space is trusted to know better than the driver whether D3cold is
working.

That feels unsafe and wrong.  Assume that the change was introduced
inadvertently and do not overwrite no_d3cold when d3cold_allowed is
modified.  Instead, consider d3cold_allowed in addition to no_d3cold
when choosing a suspend state for the device.

That way, user space may opt out of D3cold if the driver hasn't, but it
may no longer force an opt in if the driver has opted out.

Fixes: 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
Link: https://lore.kernel.org/r/b8a7f4af2b73f6b506ad8ddee59d747cbf834606.1695025365.git.lukas@wunner.de
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Cc: stable@vger.kernel.org	# v4.8+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 7aa1c20582ab864ff21876b130ca670b91f2f08e..2f5eddf03ac6a16ecb6b9106aa86ff1ce96c85a9 100644 (file)
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -911,7 +911,7 @@ pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
 {
        int acpi_state, d_max;
 
-       if (pdev->no_d3cold)
+       if (pdev->no_d3cold || !pdev->d3cold_allowed)
                d_max = ACPI_STATE_D3_HOT;
        else
                d_max = ACPI_STATE_D3_COLD;

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 6ccd88d1bfa0fc49d9298a0b6a8aa132e20fa16f..df1c44a5c886c5135cb04904517afbb6acd06318 100644 (file)
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -529,10 +529,7 @@ static ssize_t d3cold_allowed_store(struct device *dev,
                return -EINVAL;
 
        pdev->d3cold_allowed = !!val;
-       if (pdev->d3cold_allowed)
-               pci_d3cold_enable(pdev);
-       else
-               pci_d3cold_disable(pdev);
+       pci_bridge_d3_update(pdev);
 
        pm_runtime_resume(dev);